Netcode Issue(?)

Description

A clear and concise description of what the bug is.

Reproduce Steps

When Hosting
NullReferenceException: Object reference not set to an instance of an object
Unity.Netcode.ListSerializer1[T].Duplicate (System.Collections.Generic.List1[T]& value, System.Collections.Generic.List1[T]& duplicatedValue) (at ./Library/PackageCache/com.unity.netcode.gameobjects@bd2a018756ed/Runtime/NetworkVariable/Serialization/TypedSerializerImplementations.cs:344) Unity.Netcode.ListSerializer1[T].Unity.Netcode.INetworkVariableSerializer<System.Collections.Generic.List>.Duplicate (System.Collections.Generic.List1[T]& value, System.Collections.Generic.List1[T]& duplicatedValue) (at <638f8b09672547aea8c59a993b0e0e73>:0)
Unity.Netcode.NetworkVariableSerialization1[T].Duplicate (T& value, T& duplicatedValue) (at ./Library/PackageCache/com.unity.netcode.gameobjects@bd2a018756ed/Runtime/NetworkVariable/Serialization/NetworkVariableSerialization.cs:155) Unity.Netcode.NetworkVariable1[T].OnInitialize () (at ./Library/PackageCache/com.unity.netcode.gameobjects@bd2a018756ed/Runtime/NetworkVariable/NetworkVariable.cs:60)
Unity.Netcode.NetworkVariableBase.Initialize (Unity.Netcode.NetworkBehaviour networkBehaviour) (at ./Library/PackageCache/com.unity.netcode.gameobjects@bd2a018756ed/Runtime/NetworkVariable/NetworkVariableBase.cs:125)
Chat.__initializeVariables () (at <1c349474cc5642378be2cfec158ae21f>:0)
Unity.Netcode.NetworkBehaviour.InitializeVariables () (at ./Library/PackageCache/com.unity.netcode.gameobjects@bd2a018756ed/Runtime/Core/NetworkBehaviour.cs:1019)
Unity.Netcode.NetworkBehaviour.InternalOnNetworkSpawn () (at ./Library/PackageCache/com.unity.netcode.gameobjects@bd2a018756ed/Runtime/Core/NetworkBehaviour.cs:789)
Unity.Netcode.NetworkObject.InvokeBehaviourNetworkSpawn () (at ./Library/PackageCache/com.unity.netcode.gameobjects@bd2a018756ed/Runtime/Core/NetworkObject.cs:2566)
Unity.Netcode.NetworkSpawnManager.SpawnNetworkObjectLocallyCommon (Unity.Netcode.NetworkObject networkObject, System.UInt64 networkId, System.Boolean sceneObject, System.Boolean playerObject, System.UInt64 ownerClientId, System.Boolean destroyWithScene) (at ./Library/PackageCache/com.unity.netcode.gameobjects@bd2a018756ed/Runtime/Spawning/NetworkSpawnManager.cs:1197)
Unity.Netcode.NetworkSpawnManager.AuthorityLocalSpawn (Unity.Netcode.NetworkObject networkObject, System.UInt64 networkId, System.Boolean sceneObject, System.Boolean playerObject, System.UInt64 ownerClientId, System.Boolean destroyWithScene) (at ./Library/PackageCache/com.unity.netcode.gameobjects@bd2a018756ed/Runtime/Spawning/NetworkSpawnManager.cs:1093)
Unity.Netcode.NetworkSpawnManager.ServerSpawnSceneObjectsOnStartSweep () (at ./Library/PackageCache/com.unity.netcode.gameobjects@bd2a018756ed/Runtime/Spawning/NetworkSpawnManager.cs:1505)
Unity.Netcode.NetworkManager.HostServerInitialize () (at ./Library/PackageCache/com.unity.netcode.gameobjects@bd2a018756ed/Runtime/Core/NetworkManager.cs:1481)
Unity.Netcode.NetworkManager.StartHost () (at ./Library/PackageCache/com.unity.netcode.gameobjects@bd2a018756ed/Runtime/Core/NetworkManager.cs:1437)
UnityEngine.Debug:LogException(Exception)
Unity.Netcode.NetworkManager:StartHost() (at ./Library/PackageCache/com.unity.netcode.gameobjects@bd2a018756ed/Runtime/Core/NetworkManager.cs:1442)
Buttons:Host() (at Assets/Scripts/GameState/Buttons.cs:11)
UnityEngine.EventSystems.EventSystem:Update() (at ./Library/PackageCache/com.unity.ugui@f33505fcd0e6/Runtime/UGUI/EventSystem/EventSystem.cs:514)

When trying to join as a client
[Netcode] A ConnectionRequestMessage was received from the server on the client side. NetworkTransport: Unity.Netcode.Transports.UTP.UnityTransport UnityTransportProtocol: UnityTransport. This should not happen. Please report this to the Netcode for GameObjects team at https://github.com/Unity-Technologies/com.unity.netcode.gameobjects/issues and include the following data: Message Size: 170. Message Content: 02 02 7d 9a e2 a5 21 b2 36 17 b3 11 46 c4 ca 04 01 2a b2 f1 50 01 e9 3a b6 d2 01 39 3b e8 2c 01 ab c9 50 60 01 53 a3 38 44 21 d3 f6 1c b8 01 7f 10 0d af 01 f3 a2 4a 4a 01 a6 22 89 97 01 e9 4e 31 0d 01 b5 fe 01 74 11 be 97 be 73 01 bd 23 d8 d0 01 58 aa fb 1c 01 9d 9a 5c 01 01 e9 51 97 17 01 8a f7 e7 83 01 ee 80 1f c6 01 42 7f 88 c6 01 97 a3 f5 46 01 c2 40 2e a3 01 4e 67 03 d2 01 00 00 00 00 01 00 00 00 00 01 00 00 00 00 01 00 00 00 00 01 00 00 00 00 01 00 00 00 00 01 00 00 00 00 01 7b b0 63 b4 84 16 87 b7
UnityEngine.Debug:LogError (object)
Unity.Netcode.NetworkLog:LogError (string) (at ./Library/PackageCache/com.unity.netcode.gameobjects@bd2a018756ed/Runtime/Logging/NetworkLog.cs:34)
Unity.Netcode.NetworkManagerHooks:OnVerifyCanReceive (ulong,System.Type,Unity.Netcode.FastBufferReader,Unity.Netcode.NetworkContext&) (at ./Library/PackageCache/com.unity.netcode.gameobjects@bd2a018756ed/Runtime/Messaging/NetworkManagerHooks.cs:95)
Unity.Netcode.NetworkMessageManager:CanReceive (ulong,System.Type,Unity.Netcode.FastBufferReader,Unity.Netcode.NetworkContext&) (at ./Library/PackageCache/com.unity.netcode.gameobjects@bd2a018756ed/Runtime/Messaging/NetworkMessageManager.cs:315)
Unity.Netcode.NetworkMessageManager:HandleMessage (Unity.Netcode.NetworkMessageHeader&,Unity.Netcode.FastBufferReader,ulong,single,int) (at ./Library/PackageCache/com.unity.netcode.gameobjects@bd2a018756ed/Runtime/Messaging/NetworkMessageManager.cs:397)
Unity.Netcode.NetworkMessageManager:ProcessIncomingMessageQueue () (at ./Library/PackageCache/com.unity.netcode.gameobjects@bd2a018756ed/Runtime/Messaging/NetworkMessageManager.cs:448)
Unity.Netcode.NetworkManager:NetworkUpdate (Unity.Netcode.NetworkUpdateStage) (at ./Library/PackageCache/com.unity.netcode.gameobjects@bd2a018756ed/Runtime/Core/NetworkManager.cs:349)
Unity.Netcode.NetworkUpdateLoop:RunNetworkUpdateStage (Unity.Netcode.NetworkUpdateStage) (at ./Library/PackageCache/com.unity.netcode.gameobjects@bd2a018756ed/Runtime/Core/NetworkUpdateLoop.cs:191)
Unity.Netcode.NetworkUpdateLoop/NetworkEarlyUpdate/<>c:b__0_0 () (at ./Library/PackageCache/com.unity.netcode.gameobjects@bd2a018756ed/Runtime/Core/NetworkUpdateLoop.cs:214)

Actual Outcome

When hosting player spawns as normal, but when trying to make a build join as a client, it won't join.

Expected Outcome

To be able to join as a client.

Screenshots

If applicable, add screenshots to help explain your problem.

Environment

OS: Windows
Unity Version: 6000.2.3f1
Netcode Version: 2.7.0 · October 31, 2025
Netcode Commit: (com.unity.netcode.gameobjects) ??
- Netcode Topology: [e.g. Client-Server, Distributed Authority, etc.]
  -Unity Transport: 2.6.0
  -Mono Cecil: 1.11.4

Additional Context

Add any other context about the problem here. Logs, code snippets would be useful here but please also consider attaching a minimal Unity project that reproduces the issue.

Thanks for reporting this! Could you try updating to the latest version of Netcode for GameObjects (v2.10.0). There's a fix in that release that could resolve your issue.

Posting this to give reference to the slight shift in numbers due to the update.
NullReferenceException: Object reference not set to an instance of an object
Unity.Netcode.ListSerializer1[T].Duplicate (System.Collections.Generic.List1[T]& value, System.Collections.Generic.List1[T]& duplicatedValue) (at ./Library/PackageCache/com.unity.netcode.gameobjects@c690afa8ab6e/Runtime/NetworkVariable/Serialization/TypedSerializerImplementations.cs:344) Unity.Netcode.ListSerializer1[T].Unity.Netcode.INetworkVariableSerializer<System.Collections.Generic.List>.Duplicate (System.Collections.Generic.List1[T]& value, System.Collections.Generic.List1[T]& duplicatedValue) (at <76fb2b6ce3064b70b1cc6a280f3a331a>:0)
Unity.Netcode.NetworkVariableSerialization1[T].Duplicate (T& value, T& duplicatedValue) (at ./Library/PackageCache/com.unity.netcode.gameobjects@c690afa8ab6e/Runtime/NetworkVariable/Serialization/NetworkVariableSerialization.cs:155) Unity.Netcode.NetworkVariable1[T].OnInitialize () (at ./Library/PackageCache/com.unity.netcode.gameobjects@c690afa8ab6e/Runtime/NetworkVariable/NetworkVariable.cs:60)
Unity.Netcode.NetworkVariableBase.Initialize (Unity.Netcode.NetworkBehaviour networkBehaviour) (at ./Library/PackageCache/com.unity.netcode.gameobjects@c690afa8ab6e/Runtime/NetworkVariable/NetworkVariableBase.cs:127)
Chat.__initializeVariables () (at :0)
Unity.Netcode.NetworkBehaviour.InitializeVariables () (at ./Library/PackageCache/com.unity.netcode.gameobjects@c690afa8ab6e/Runtime/Core/NetworkBehaviour.cs:1134)
Unity.Netcode.NetworkBehaviour.InternalOnNetworkSpawn () (at ./Library/PackageCache/com.unity.netcode.gameobjects@c690afa8ab6e/Runtime/Core/NetworkBehaviour.cs:802)
Unity.Netcode.NetworkObject.InvokeBehaviourNetworkSpawn () (at ./Library/PackageCache/com.unity.netcode.gameobjects@c690afa8ab6e/Runtime/Core/NetworkObject.cs:2542)
Unity.Netcode.NetworkSpawnManager.SpawnNetworkObjectLocallyCommon (Unity.Netcode.NetworkObject networkObject, System.UInt64 networkId, System.Boolean sceneObject, System.Boolean playerObject, System.UInt64 ownerClientId, System.Boolean destroyWithScene) (at ./Library/PackageCache/com.unity.netcode.gameobjects@c690afa8ab6e/Runtime/Spawning/NetworkSpawnManager.cs:1208)
Unity.Netcode.NetworkSpawnManager.AuthorityLocalSpawn (Unity.Netcode.NetworkObject networkObject, System.UInt64 networkId, System.Boolean sceneObject, System.Boolean playerObject, System.UInt64 ownerClientId, System.Boolean destroyWithScene) (at ./Library/PackageCache/com.unity.netcode.gameobjects@c690afa8ab6e/Runtime/Spawning/NetworkSpawnManager.cs:1104)
Unity.Netcode.NetworkSpawnManager.ServerSpawnSceneObjectsOnStartSweep () (at ./Library/PackageCache/com.unity.netcode.gameobjects@c690afa8ab6e/Runtime/Spawning/NetworkSpawnManager.cs:1507)
Unity.Netcode.NetworkManager.HostServerInitialize () (at ./Library/PackageCache/com.unity.netcode.gameobjects@c690afa8ab6e/Runtime/Core/NetworkManager.cs:1511)
Unity.Netcode.NetworkManager.StartHost () (at ./Library/PackageCache/com.unity.netcode.gameobjects@c690afa8ab6e/Runtime/Core/NetworkManager.cs:1466)
UnityEngine.Debug:LogException(Exception)
Unity.Netcode.NetworkManager:StartHost() (at ./Library/PackageCache/com.unity.netcode.gameobjects@c690afa8ab6e/Runtime/Core/NetworkManager.cs:1471)
Buttons:Host() (at Assets/Scripts/GameState/Buttons.cs:11)
UnityEngine.EventSystems.EventSystem:Update() (at ./Library/PackageCache/com.unity.ugui@f33505fcd0e6/Runtime/UGUI/EventSystem/EventSystem.cs:514)

Client Connect Error message disappeared, joining as a client still doesn't work.

Do you mind sharing more details about the problem. Are there any errors that are logged on the server or the client when the client joins?

Try setting your NetworkManager.LogLevel to LogLevel.Developer to see if that gives more detail to find the issue.

The second stack trace you have posted looks like there's a NetworkVariable containing a nested list where one of the nested list elements is set to null instead of a list.

Note that this is from an attempt to host and that no code of mine called shutdown

(Debug)[Netcode] StartHost
UnityEngine.Debug:Log (object)
Unity.Netcode.NetworkLog:LogInfo (string) (at ./Library/PackageCache/com.unity.netcode.gameobjects@c690afa8ab6e/Runtime/Logging/NetworkLog.cs:22)
Unity.Netcode.NetworkManager:StartHost () (at ./Library/PackageCache/com.unity.netcode.gameobjects@c690afa8ab6e/Runtime/Core/NetworkManager.cs:1430)
Buttons:Host () (at Assets/Scripts/GameState/Buttons.cs:11)
UnityEngine.EventSystems.EventSystem:Update () (at ./Library/PackageCache/com.unity.ugui@f33505fcd0e6/Runtime/UGUI/EventSystem/EventSystem.cs:514)

(Debug)[Netcode] Initialize
UnityEngine.Debug:Log (object)
Unity.Netcode.NetworkLog:LogInfo (string) (at ./Library/PackageCache/com.unity.netcode.gameobjects@c690afa8ab6e/Runtime/Logging/NetworkLog.cs:22)
Unity.Netcode.NetworkManager:Initialize (bool) (at ./Library/PackageCache/com.unity.netcode.gameobjects@c690afa8ab6e/Runtime/Core/NetworkManager.cs:1184)
Unity.Netcode.NetworkManager:StartHost () (at ./Library/PackageCache/com.unity.netcode.gameobjects@c690afa8ab6e/Runtime/Core/NetworkManager.cs:1445)
Buttons:Host () (at Assets/Scripts/GameState/Buttons.cs:11)
UnityEngine.EventSystems.EventSystem:Update () (at ./Library/PackageCache/com.unity.ugui@f33505fcd0e6/Runtime/UGUI/EventSystem/EventSystem.cs:514)

(Debug)[Netcode] [Server-Side] Pending Client-0 connection approved!
UnityEngine.Debug:Log (object)
Unity.Netcode.NetworkLog:LogInfo (string) (at ./Library/PackageCache/com.unity.netcode.gameobjects@c690afa8ab6e/Runtime/Logging/NetworkLog.cs:22)
Unity.Netcode.NetworkConnectionManager:HandleConnectionApproval (ulong,bool,System.Nullable1<uint>,System.Nullable1<UnityEngine.Vector3>,System.Nullable`1<UnityEngine.Quaternion>) (at ./Library/PackageCache/com.unity.netcode.gameobjects@c690afa8ab6e/Runtime/Connection/NetworkConnectionManager.cs:959)
Unity.Netcode.NetworkManager:HostServerInitialize () (at ./Library/PackageCache/com.unity.netcode.gameobjects@c690afa8ab6e/Runtime/Core/NetworkManager.cs:1508)
Unity.Netcode.NetworkManager:StartHost () (at ./Library/PackageCache/com.unity.netcode.gameobjects@c690afa8ab6e/Runtime/Core/NetworkManager.cs:1466)
Buttons:Host () (at Assets/Scripts/GameState/Buttons.cs:11)
UnityEngine.EventSystems.EventSystem:Update () (at ./Library/PackageCache/com.unity.ugui@f33505fcd0e6/Runtime/UGUI/EventSystem/EventSystem.cs:514)

(Error)NullReferenceException: Object reference not set to an instance of an object
Unity.Netcode.ListSerializer1[T].Duplicate (System.Collections.Generic.List1[T]& value, System.Collections.Generic.List1[T]& duplicatedValue) (at ./Library/PackageCache/com.unity.netcode.gameobjects@c690afa8ab6e/Runtime/NetworkVariable/Serialization/TypedSerializerImplementations.cs:344) Unity.Netcode.ListSerializer1[T].Unity.Netcode.INetworkVariableSerializer<System.Collections.Generic.List>.Duplicate (System.Collections.Generic.List1[T]& value, System.Collections.Generic.List1[T]& duplicatedValue) (at <76fb2b6ce3064b70b1cc6a280f3a331a>:0)
Unity.Netcode.NetworkVariableSerialization1[T].Duplicate (T& value, T& duplicatedValue) (at ./Library/PackageCache/com.unity.netcode.gameobjects@c690afa8ab6e/Runtime/NetworkVariable/Serialization/NetworkVariableSerialization.cs:155) Unity.Netcode.NetworkVariable1[T].OnInitialize () (at ./Library/PackageCache/com.unity.netcode.gameobjects@c690afa8ab6e/Runtime/NetworkVariable/NetworkVariable.cs:60)
Unity.Netcode.NetworkVariableBase.Initialize (Unity.Netcode.NetworkBehaviour networkBehaviour) (at ./Library/PackageCache/com.unity.netcode.gameobjects@c690afa8ab6e/Runtime/NetworkVariable/NetworkVariableBase.cs:127)
Chat.__initializeVariables () (at :0)
Unity.Netcode.NetworkBehaviour.InitializeVariables () (at ./Library/PackageCache/com.unity.netcode.gameobjects@c690afa8ab6e/Runtime/Core/NetworkBehaviour.cs:1134)
Unity.Netcode.NetworkBehaviour.InternalOnNetworkSpawn () (at ./Library/PackageCache/com.unity.netcode.gameobjects@c690afa8ab6e/Runtime/Core/NetworkBehaviour.cs:802)
Unity.Netcode.NetworkObject.InvokeBehaviourNetworkSpawn () (at ./Library/PackageCache/com.unity.netcode.gameobjects@c690afa8ab6e/Runtime/Core/NetworkObject.cs:2542)
Unity.Netcode.NetworkSpawnManager.SpawnNetworkObjectLocallyCommon (Unity.Netcode.NetworkObject networkObject, System.UInt64 networkId, System.Boolean sceneObject, System.Boolean playerObject, System.UInt64 ownerClientId, System.Boolean destroyWithScene) (at ./Library/PackageCache/com.unity.netcode.gameobjects@c690afa8ab6e/Runtime/Spawning/NetworkSpawnManager.cs:1208)
Unity.Netcode.NetworkSpawnManager.AuthorityLocalSpawn (Unity.Netcode.NetworkObject networkObject, System.UInt64 networkId, System.Boolean sceneObject, System.Boolean playerObject, System.UInt64 ownerClientId, System.Boolean destroyWithScene) (at ./Library/PackageCache/com.unity.netcode.gameobjects@c690afa8ab6e/Runtime/Spawning/NetworkSpawnManager.cs:1104)
Unity.Netcode.NetworkSpawnManager.ServerSpawnSceneObjectsOnStartSweep () (at ./Library/PackageCache/com.unity.netcode.gameobjects@c690afa8ab6e/Runtime/Spawning/NetworkSpawnManager.cs:1507)
Unity.Netcode.NetworkManager.HostServerInitialize () (at ./Library/PackageCache/com.unity.netcode.gameobjects@c690afa8ab6e/Runtime/Core/NetworkManager.cs:1511)
Unity.Netcode.NetworkManager.StartHost () (at ./Library/PackageCache/com.unity.netcode.gameobjects@c690afa8ab6e/Runtime/Core/NetworkManager.cs:1466)
UnityEngine.Debug:LogException(Exception)
Unity.Netcode.NetworkManager:StartHost() (at ./Library/PackageCache/com.unity.netcode.gameobjects@c690afa8ab6e/Runtime/Core/NetworkManager.cs:1471)
Buttons:Host() (at Assets/Scripts/GameState/Buttons.cs:11)
UnityEngine.EventSystems.EventSystem:Update() (at ./Library/PackageCache/com.unity.ugui@f33505fcd0e6/Runtime/UGUI/EventSystem/EventSystem.cs:514)

(Debug)[Netcode] ShutdownInternal
UnityEngine.Debug:Log (object)
Unity.Netcode.NetworkLog:LogInfo (string) (at ./Library/PackageCache/com.unity.netcode.gameobjects@c690afa8ab6e/Runtime/Logging/NetworkLog.cs:22)
Unity.Netcode.NetworkManager:ShutdownInternal () (at ./Library/PackageCache/com.unity.netcode.gameobjects@c690afa8ab6e/Runtime/Core/NetworkManager.cs:1610)
Unity.Netcode.NetworkManager:StartHost () (at ./Library/PackageCache/com.unity.netcode.gameobjects@c690afa8ab6e/Runtime/Core/NetworkManager.cs:1473)
Buttons:Host () (at Assets/Scripts/GameState/Buttons.cs:11)
UnityEngine.EventSystems.EventSystem:Update () (at ./Library/PackageCache/com.unity.ugui@f33505fcd0e6/Runtime/UGUI/EventSystem/EventSystem.cs:514)

(Warning)[Netcode] Trying to destroy object 0 but it doesn't seem to exist anymore!
UnityEngine.Debug:LogWarning (object)
Unity.Netcode.NetworkLog:LogWarning (string) (at ./Library/PackageCache/com.unity.netcode.gameobjects@c690afa8ab6e/Runtime/Logging/NetworkLog.cs:28)
Unity.Netcode.NetworkSpawnManager:OnDespawnObject (Unity.Netcode.NetworkObject,bool,bool) (at ./Library/PackageCache/com.unity.netcode.gameobjects@c690afa8ab6e/Runtime/Spawning/NetworkSpawnManager.cs:1576)
Unity.Netcode.NetworkSpawnManager:DespawnAndDestroyNetworkObjects () (at ./Library/PackageCache/com.unity.netcode.gameobjects@c690afa8ab6e/Runtime/Spawning/NetworkSpawnManager.cs:1452)
Unity.Netcode.NetworkManager:ShutdownInternal () (at ./Library/PackageCache/com.unity.netcode.gameobjects@c690afa8ab6e/Runtime/Core/NetworkManager.cs:1650)
Unity.Netcode.NetworkManager:StartHost () (at ./Library/PackageCache/com.unity.netcode.gameobjects@c690afa8ab6e/Runtime/Core/NetworkManager.cs:1473)
Buttons:Host () (at Assets/Scripts/GameState/Buttons.cs:11)
UnityEngine.EventSystems.EventSystem:Update () (at ./Library/PackageCache/com.unity.ugui@f33505fcd0e6/Runtime/UGUI/EventSystem/EventSystem.cs:514)

(Debug)[Netcode] [Disconnect Event][Client-0][TransportClientId-0][TransportShutdown] NetworkConnectionManager was shutdown. The transport was shutdown.
UnityEngine.Debug:Log (object)
Unity.Netcode.NetworkLog:LogInfo (string) (at ./Library/PackageCache/com.unity.netcode.gameobjects@c690afa8ab6e/Runtime/Logging/NetworkLog.cs:22)
Unity.Netcode.NetworkConnectionManager:GenerateDisconnectInformation (ulong,ulong,string) (at ./Library/PackageCache/com.unity.netcode.gameobjects@c690afa8ab6e/Runtime/Connection/NetworkConnectionManager.cs:614)
Unity.Netcode.NetworkConnectionManager:Shutdown () (at ./Library/PackageCache/com.unity.netcode.gameobjects@c690afa8ab6e/Runtime/Connection/NetworkConnectionManager.cs:1599)
Unity.Netcode.NetworkManager:ShutdownInternal () (at ./Library/PackageCache/com.unity.netcode.gameobjects@c690afa8ab6e/Runtime/Core/NetworkManager.cs:1658)
Unity.Netcode.NetworkManager:StartHost () (at ./Library/PackageCache/com.unity.netcode.gameobjects@c690afa8ab6e/Runtime/Core/NetworkManager.cs:1473)
Buttons:Host () (at Assets/Scripts/GameState/Buttons.cs:11)
UnityEngine.EventSystems.EventSystem:Update () (at ./Library/PackageCache/com.unity.ugui@f33505fcd0e6/Runtime/UGUI/EventSystem/EventSystem.cs:514)

(Warning)Directly calling UnityTransport.Shutdown() results in unexpected shutdown behaviour. All pending events will be lost. Use NetworkManager.Shutdown() instead.
UnityEngine.Debug:LogWarning (object)
Unity.Netcode.Transports.UTP.UnityTransport:Shutdown () (at ./Library/PackageCache/com.unity.netcode.gameobjects@c690afa8ab6e/Runtime/Transports/UTP/UnityTransport.cs:1714)
Unity.Netcode.NetworkConnectionManager:Shutdown () (at ./Library/PackageCache/com.unity.netcode.gameobjects@c690afa8ab6e/Runtime/Connection/NetworkConnectionManager.cs:1681)
Unity.Netcode.NetworkManager:ShutdownInternal () (at ./Library/PackageCache/com.unity.netcode.gameobjects@c690afa8ab6e/Runtime/Core/NetworkManager.cs:1658)
Unity.Netcode.NetworkManager:StartHost () (at ./Library/PackageCache/com.unity.netcode.gameobjects@c690afa8ab6e/Runtime/Core/NetworkManager.cs:1473)
Buttons:Host () (at Assets/Scripts/GameState/Buttons.cs:11)
UnityEngine.EventSystems.EventSystem:Update () (at ./Library/PackageCache/com.unity.ugui@f33505fcd0e6/Runtime/UGUI/EventSystem/EventSystem.cs:514)

(Debug)[Netcode] NetworkConnectionManager.Shutdown() -> IsListening && NetworkTransport != null -> NetworkTransport.Shutdown()
UnityEngine.Debug:Log (object)
Unity.Netcode.NetworkLog:LogInfo (string) (at ./Library/PackageCache/com.unity.netcode.gameobjects@c690afa8ab6e/Runtime/Logging/NetworkLog.cs:22)
Unity.Netcode.NetworkConnectionManager:Shutdown () (at ./Library/PackageCache/com.unity.netcode.gameobjects@c690afa8ab6e/Runtime/Connection/NetworkConnectionManager.cs:1684)
Unity.Netcode.NetworkManager:ShutdownInternal () (at ./Library/PackageCache/com.unity.netcode.gameobjects@c690afa8ab6e/Runtime/Core/NetworkManager.cs:1658)
Unity.Netcode.NetworkManager:StartHost () (at ./Library/PackageCache/com.unity.netcode.gameobjects@c690afa8ab6e/Runtime/Core/NetworkManager.cs:1473)
Buttons:Host () (at Assets/Scripts/GameState/Buttons.cs:11)
UnityEngine.EventSystems.EventSystem:Update () (at ./Library/PackageCache/com.unity.ugui@f33505fcd0e6/Runtime/UGUI/EventSystem/EventSystem.cs:514)

@Magman3000

Hi @Magman3000,

This looks like there could be an issue with one of your NetworkVariables.
How many declared NetworkVariable<List<T>> fields do you have?
If only a few, could you post the script (or portions of it) where you are:

Declaring it.
Using/accessing it.

If the type T in your list is an INetworkSerializable then could you post that too?

Also, did you have developer logging enabled in NetworkManager when generating those logs? If not, then go ahead and enable that, re-run, and post the logs generated. That should get some additional details that could help track down the specific NetworkVariable<List<T>> field that is causing the issue.

It looks like it could not be getting assigned.

Things to look for:

    // This could be problematic
    private NetworkVariable<List<int>> m_NetworkVariable1;

    // This could be problematic (no default internal list defined)
    private NetworkVariable<List<int>> m_NetworkVariable2 = new NetworkVariable<List<int>>();

    /// <summary>
    /// Recommended way is to assign a new instance when it is declared with the default (i.e. empy list)
    /// </summary>
    private NetworkVariable<List<int>> m_NetworkVariable3 = new NetworkVariable<List<int>>(default);

Let me know if you find the issue or please post back the additional information so we can help you find it.

Tested Commenting out the code on this component instead of toggling the component disabled out of paranoia, and things started working, so I guess that's a fix, but it affecting things without being active feels weird.

[SerializeField] private GameObject chatPanel, textObject;
private NetworkVariable<List<string>> entries = new NetworkVariable<List<string>>();

public void AddEntry(string playerName, string message)
{   
    entries.Value.Add(playerName + ": " + message);
    
}

Ah yes, if you have a NetworkVariable<List<string>> that's never initialized, then trying to add to the list will fail because the List is null. new NetworkVariable<List<string>>() initializes the NetworkVariable but not the underlying List. To initialize the underlying list you can use new NetworkVariable<List<string>>(new List<string>()).

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Netcode Issue(?) #3888

Description

Reproduce Steps

Actual Outcome

Expected Outcome

Screenshots

Environment

Additional Context

Note that this is from an attempt to host and that no code of mine called shutdown

1 remaining item

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Netcode Issue(?) #3888

Description

Description

Reproduce Steps

Actual Outcome

Expected Outcome

Screenshots

Environment

Additional Context

Activity

EmandM commented on Mar 5, 2026

Magman3000 commented on Mar 6, 2026

Magman3000 commented on Mar 6, 2026

EmandM commented on Mar 6, 2026

Magman3000 commented on Mar 6, 2026

Note that this is from an attempt to host and that no code of mine called shutdown

1 remaining item

NoelStephensUnity commented on Mar 6, 2026

Magman3000 commented on Mar 7, 2026

EmandM commented on Mar 9, 2026

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