NullReferenceException: Object reference not set to an instance of an object
  at BuildingBlock.GetGrade (BuildingGrade+Enum iGrade) [0x00000] in <480bce7997314352ad66a6bd12794838>:0 
  at BuildingBlock.get_currentGrade () [0x00000] in <480bce7997314352ad66a6bd12794838>:0 
  at BuildingBlock.ChangeSkin () [0x00009] in <480bce7997314352ad66a6bd12794838>:0 
  at BuildingBlock.UpdateSkin (System.Boolean force) [0x00028] in <480bce7997314352ad66a6bd12794838>:0 
  at SaveRestore.InitializeEntityConditionals () [0x00086] in <480bce7997314352ad66a6bd12794838>:0 
  at Bootstrap+<StartServer>d__19.MoveNext () [0x0027a] in <480bce7997314352ad66a6bd12794838>:0 
  at UnityEngine.SetupCoroutine.InvokeMoveNext (System.Collections.IEnumerator enumerator, System.IntPtr returnValueAddress) [0x00026] in <0618f269b594493b97c56ba78f03373a>:0 
 
(Filename: <480bce7997314352ad66a6bd12794838> Line: 0)​

Thanks


edit: I've removed the plugin for try and it's same, server is stuck with this error :( :x

Found the problem, it's removertool...