The problem is that error occurs when client disconnect with NetworkObject pooling.

[kaygundraka]

Excuse me, guys.
I met a big problem using Netcode 1.0.0-pre.9
The problem is that error occurs when client disconnect with NetworkObject pooling.
The reason why this error occurs,

1. 'Observers' in NetworkObject add when NetworkObject spawn or client connect, but doesn't remove when NetworkObject despawned.
2. So if you pool NetworkObject, 'Observers' in pooled NetworkObject( == despawned NetworkObject) still has clientId (although client disconnect)
3. When pooled NetworkObject respawn, they use unreliable clientIds. If that client disconnect, they make an error.

KeyNotFoundException: The given key was not present in the dictionary.
System.Collections.Generic.Dictionary2[TKey,TValue].get_Item (TKey key) (at <695d1cc93cca45069c528c15c9fdd749>:0)
Unity.Netcode.MessagingSystem.SendPreSerializedMessage[TMessageType] (Unity.Netcode.FastBufferWriter& tmpSerializer, System.Int32 maxSize, TMessageType& message, Unity.Netcode.NetworkDelivery delivery, System.Collections.Generic.IReadOnlyList1[System.UInt64]& clientIds) (at Library/PackageCache/com.unity.netcode.gameobjects@1.0.0-pre.9/Runtime/Messaging/MessagingSystem.cs:405)

4. I think that the solution is adding networkObject.Observers.Clear() to NetworkSpawnManager.cs (line 528). It means that before NetworkObject respawn, clear obeservers.
   I solved this problem temporarily like this (because only method to remove observers is NetworkHide function)

foreach (var id in NetworkManager.Singleton.ConnectedClientsIds)
{
if (id == NetworkManager.ServerClientId)
continue;

obj.GetComponent<NetworkObject>().NetworkHide(id);

}

obj.GetComponent().Despawn(false);
Please fix this problem as soon as possible!

[ashwinimurt]

Hi @kaygundraka
Fix for this issue was merged recently #2009
It will be part of the next release.
Could you try develop and let us know if its fixed. Thanks.
cc @NoelStephensUnity

[NoelStephensUnity]

This was fixed in PR-2009