Why do i get NullReferenceException: Object reference not set to an instance of an object

I trying to use SyncListString and get this error. However, when i check all seems to be available for access. I have tried to solve this for a few weeks now and I am totally confused.

SyncListString is available and have records
I create and populate the SyncList in something i call "MP_GameEngine" in "OnStartServer" and it all seems to work fine.

In MP_GameEngine, extracts:

Code (CSharp):

1. public SyncListString NameSyncList = new SyncListString();
2.  
3.  
4. public override void OnStartServer() {
5.     NameSyncList.Callback += ReorderCallback;
6.  
7. // Populating the SyncList
8.     for (int x = 0; x < 5; x++) {
9.         aThing = names_List [x];
10.         NameSyncList.Add (aThing);
11.         PrepareForSpawn (aThing);
12.     }

Definition in Player:

Code (CSharp):

1. public MP_GameEngine _engine;

I have this code on the player that is triggered when clicking on an object, the purpose is to move the clicked object to the top of the SyncList:

Code (CSharp):

1. void CheckAndFixSortOrder (string _name) {
2.  
3.         if (_engine.NameSyncList == null) {
4.              print("_engine.NameSyncList=NULL"+_name);
5.         } else {
6.              print("_engine.NameSyncList=EXISTS"+_name);
7.         }
8.  
9.         print ("#2: " + _engine.NameSyncList [2]);
10.  
11.         Cmd_RemoveSyncList(_name);
12.         Cmd_AddSyncList (_name);
13.         //FixSortOrder ();
14.         _engine.FixSortingOrder();
15.     }
16.  
17.     [Command]
18.     void Cmd_AddSyncList (string _name) {
19.         _engine.NameSyncList.Add (_name);
20.     }
21.  
22.     [Command]
23.     void Cmd_RemoveSyncList (string _name) {
24.         _engine.NameSyncList.Remove (_name); //<<<<<<<<<<<< ERROR
25.     }

The print's give the following output:

Code (CSharp):

1. _engine.NameSyncList = EXISTS Enemy1
2.  
3. #2: Enemy3

Given that all components seems to be in place and accessible i do not understand why i get the "Object reference not set to an instance of an object" message?

I get the following Error messages:

Code (CSharp):

1. NullReferenceException: Object reference not set to an instance of an object
2. Player.Cmd_RemoveSyncList (System.String _name) (at Assets/Multiplayer/Scripts UNET/Player.cs:218)
3. Player.InvokeCmdCmd_RemoveSyncList (UnityEngine.Networking.NetworkBehaviour obj, UnityEngine.Networking.NetworkReader reader)
4. UnityEngine.Networking.NetworkIdentity.HandleCommand (Int32 cmdHash, UnityEngine.Networking.NetworkReader reader) (at /Users/builduser/buildslave/unity/build/Extensions/Networking/Runtime/NetworkIdentity.cs:616)
5. UnityEngine.Networking.NetworkServer.OnCommandMessage (UnityEngine.Networking.NetworkMessage netMsg) (at /Users/builduser/buildslave/unity/build/Extensions/Networking/Runtime/NetworkServer.cs:1298)
6. UnityEngine.Networking.NetworkConnection.HandleReader (UnityEngine.Networking.NetworkReader reader, Int32 receivedSize, Int32 channelId) (at /Users/builduser/buildslave/unity/build/Extensions/Networking/Runtime/NetworkConnection.cs:468)
7. UnityEngine.Networking.NetworkConnection.HandleBytes (System.Byte[] buffer, Int32 receivedSize, Int32 channelId) (at /Users/builduser/buildslave/unity/build/Extensions/Networking/Runtime/NetworkConnection.cs:424)
8. UnityEngine.Networking.NetworkConnection.TransportRecieve (System.Byte[] bytes, Int32 numBytes, Int32 channelId) (at /Users/builduser/buildslave/unity/build/Extensions/Networking/Runtime/NetworkConnection.cs:576)
9. UnityEngine.Networking.NetworkServer.OnData (UnityEngine.Networking.NetworkConnection conn, Int32 receivedSize, Int32 channelId) (at /Users/builduser/buildslave/unity/build/Extensions/Networking/Runtime/NetworkServer.cs:753)
10. UnityEngine.Networking.NetworkServer+ServerSimpleWrapper.OnData (UnityEngine.Networking.NetworkConnection conn, Int32 receivedSize, Int32 channelId) (at /Users/builduser/buildslave/unity/build/Extensions/Networking/Runtime/NetworkServer.cs:1851)
11. UnityEngine.Networking.NetworkServerSimple.HandleData (Int32 connectionId, Int32 channelId, Int32 receivedSize, Byte error) (at /Users/builduser/buildslave/unity/build/Extensions/Networking/Runtime/NetworkServerSimple.cs:384)
12. UnityEngine.Networking.NetworkServerSimple.Update () (at /Users/builduser/buildslave/unity/build/Extensions/Networking/Runtime/NetworkServerSimple.cs:248)
13. UnityEngine.Networking.NetworkServer.InternalUpdate () (at /Users/builduser/buildslave/unity/build/Extensions/Networking/Runtime/NetworkServer.cs:705)
14. UnityEngine.Networking.NetworkServer.Update () (at /Users/builduser/buildslave/unity/build/Extensions/Networking/Runtime/NetworkServer.cs:655)
15. UnityEngine.Networking.NetworkIdentity.UNetStaticUpdate () (at /Users/builduser/buildslave/unity/build/Extensions/Networking/Runtime/NetworkIdentity.cs:1088)
16.