update

Possible fix for an edge case scenario during synchronization.

Author: NoelStephensUnity

com.unity.netcode.gameobjects/Runtime/SceneManagement/SceneEventData.cs

@@ -1146,24 +1146,37 @@ internal void SynchronizeSceneNetworkObjects(NetworkManager networkManager)
 
 #if UNIFIED_NETCODE
                     // TODO-UNIFIED: This is a temporary POC fix to handle synchronizing hybrid spawned objects where the Ghost instance might not yet exist.
-                    if (serializedObject.HasGhost && !networkManager.SpawnManager.GhostsPendingSpawn.ContainsKey(serializedObject.NetworkObjectId))
+                    if (serializedObject.HasGhost)
                     {
-                        if (networkManager.LogLevel == LogLevel.Developer)
+                        if (!networkManager.SpawnManager.GhostsPendingSpawn.ContainsKey(serializedObject.NetworkObjectId))
                         {
-                            UnityEngine.Debug.Log($"[{nameof(SceneEventData)}][{nameof(SynchronizeSceneNetworkObjects)}] Deferring creation of NetworkObjectId-{serializedObject.NetworkObjectId} to wait for Ghost.");
-                        }
-
-                        var newEntry = new PendingGhostSpawnEntry()
-                        {
-                            RegistrationTime = UnityEngine.Time.realtimeSinceStartup,
-                            SerializedObject = serializedObject,
-                            Buffer = new FastBufferReader(InternalBuffer, Allocator.Persistent, serializedObject.SynchronizationDataSize, InternalBuffer.Position)
-                        };
+                            if (networkManager.LogLevel == LogLevel.Developer)
+                            {
+                                UnityEngine.Debug.Log($"[{nameof(SceneEventData)}][{nameof(SynchronizeSceneNetworkObjects)}] Deferring creation of NetworkObjectId-{serializedObject.NetworkObjectId} to wait for Ghost.");
+                            }
 
-                        spawnManager.RegisterGhostPendingSynchronization(newEntry);
+                            var newEntry = new PendingGhostSpawnEntry()
+                            {
+                                RegistrationTime = UnityEngine.Time.realtimeSinceStartup,
+                                SerializedObject = serializedObject,
+                                Buffer = new FastBufferReader(InternalBuffer, Allocator.Persistent, serializedObject.SynchronizationDataSize, InternalBuffer.Position)
+                            };
 
-                        InternalBuffer.Seek(InternalBuffer.Position + serializedObject.SynchronizationDataSize);
-                        continue;
+                            spawnManager.RegisterGhostPendingSynchronization(newEntry);
+                            InternalBuffer.Seek(InternalBuffer.Position + serializedObject.SynchronizationDataSize);
+                            continue;
+                        }
+                        else if (networkManager.SpawnManager.GhostsPendingSpawn[serializedObject.NetworkObjectId] == null)
+                        {
+                            if (networkManager.LogLevel == LogLevel.Developer)
+                            {
+                                UnityEngine.Debug.Log($"[{nameof(SceneEventData)}][{nameof(SynchronizeSceneNetworkObjects)}] Dropping creation of NetworkObjectId-{serializedObject.NetworkObjectId} as it has an entry but no longer exists!");
+                            }
+                            // If it no longer exists, then just remove the entry and skip it.
+                            InternalBuffer.Seek(InternalBuffer.Position + serializedObject.SynchronizationDataSize);
+                            networkManager.SpawnManager.GhostsPendingSpawn.Remove(serializedObject.NetworkObjectId);
+                            continue;
+                        }
                     }
 #endif