Failed to call hook 'OnEntityBuilt' on plugin 'BGrade v1.0.49' (NullReferenceException: Object reference not set to an instance of an object)
  at Oxide.Plugins.BGrade.OnEntityBuilt (Planner plan, UnityEngine.GameObject gameObject) [0x00010] in <8dc4300e53bc48d4acd743fbc590a98b>:0
  at Oxide.Plugins.BGrade.DirectCallHook (System.String name, System.Object& ret, System.Object[] args) [0x003e4] in <8dc4300e53bc48d4acd743fbc590a98b>:0
  at Oxide.Plugins.CSharpPlugin.InvokeMethod (Oxide.Core.Plugins.HookMethod method, System.Object[] args) [0x00079] in <33f7c42a56934dae8ec04b11017dce31>:0
  at Oxide.Core.Plugins.CSPlugin.OnCallHook (System.String name, System.Object[] args) [0x000d8] in <33287985591c40d6983f0b8f0e915565>:0
  at Oxide.Core.Plugins.Plugin.CallHook (System.String hook, System.Object[] args) [0x00060] in <33287985591c40d6983f0b8f0e915565>:0

Please update to the latest Oxide build and let me know if you still have this issue.