Netcode Issue(?)

[Magman3000]

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.