fix: Do not propagate in-scene value to dynamically spawned children [MTT-5357]

com.unity.netcode.gameobjects/CHANGELOG.md

@@ -21,8 +21,10 @@ Additional documentation and release notes are available at [Multiplayer Documen
 - Network prefabs are now stored in a ScriptableObject that can be shared between NetworkManagers, and have been exposed for public access. By default, a Default Prefabs List is created that contains all NetworkObject prefabs in the project, and new NetworkManagers will default to using that unless that option is turned off in the Netcode for GameObjects settings. Existing NetworkManagers will maintain their existing lists, which can be migrated to the new format via a button in their inspector. (#2322)
 
 ### Fixed
+
 - Fixed issue where changes to a layer's weight would not synchronize unless a state transition was occurring.(#2399)
 - Fixed issue where `NetworkManager.LocalClientId` was returning the `NetworkTransport.ServerClientId` as opposed to the `NetworkManager.m_LocalClientId`. (#2398)
+- Fixed issue where a dynamically spawned `NetworkObject` parented under an in-scene placed `NetworkObject` would have its `InScenePlaced` value changed to `true`. This would result in a soft synchronization error for late joining clients. (#2396)
 - Fixed a UTP test that was failing when you install Unity Transport package 2.0.0 or newer. (#2347)
 - Fixed issue where `NetcodeSettingsProvider` would throw an exception in Unity 2020.3.x versions. (#2345)
 - Fixed server side issue where, depending upon component ordering, some NetworkBehaviour components might not have their OnNetworkDespawn method invoked if the client side disconnected. (#2323)

com.unity.netcode.gameobjects/Runtime/Spawning/NetworkSpawnManager.cs

@@ -603,6 +603,11 @@ private void SpawnNetworkObjectLocallyCommon(NetworkObject networkObject, ulong
             var children = networkObject.GetComponentsInChildren<NetworkObject>();
             foreach (var childObject in children)
             {
+                // Do not propagate the in-scene object setting if a child was dynamically spawned.
+                if (childObject.IsSceneObject.HasValue && !childObject.IsSceneObject.Value)
+                {
+                    continue;
+                }
                 childObject.IsSceneObject = sceneObject;
             }
         }