Failed to call hook 'OnEntityBuilt' on plugin 'BGrade v1.1.5' (NullReferenceException: Object reference not set to an instance of an object)
  at Oxide.Plugins.BGrade.OnEntityBuilt (Planner plan, UnityEngine.GameObject gameObject) [0x000cb] in <5cee32febcb74961b4bcbe32c1a49aba>:0

  at Oxide.Plugins.BGrade.DirectCallHook (System.String name, System.Object& ret, System.Object[] args) [0x004dd] in <5cee32febcb74961b4bcbe32c1a49aba>:0

  at Oxide.Plugins.CSharpPlugin.InvokeMethod (Oxide.Core.Plugins.HookMethod method, System.Object[] args) [0x00079] in <e3740cd7ab6f40909737d74eeeaf1a8a>:0

  at Oxide.Core.Plugins.CSPlugin.OnCallHook (System.String name, System.Object[] args) [0x000d8] in <032ab7611607468ebf42c14e3cf9df20>:0

  at Oxide.Core.Plugins.Plugin.CallHook (System.String hook, System.Object[] args) [0x00060] in <032ab7611607468ebf42c14e3cf9df20>:0

not sure if it's related to ohter plugin... 
can you help me?

Thanks