Wierd DC error

I have ONE player this keeps happening to. ANY ideas welcome.

 

XXX.XXX.XXX.XXX:PORT/STEAMID/PLAYERNAME disconnecting: Exception (cs:67741): NullReferenceException: Object reference not set to an instance of an object. BaseNetworkable.OnNetworkGroupChange () (at <00000000000000000000000000000000>:0) Network.Networkable.SwitchGroup (Network.Visibility.Group newGroup) (at <00000000000000000000000000000000>:0) Client.OnGroupChange (Network.Message msg) (at <00000000000000000000000000000000>:0) Client.OnNetworkMessage (Network.Message packet) (at <00000000000000000000000000000000>:0) Facepunch.Network.Raknet.Client.HandleMessage () (at <00000000000000000000000000000000>:0) Facepunch.Network.Raknet.Client.Cycle () (at <00000000000000000000000000000000>:0) Client.Update () (at <00000000000000000000000000000000>:0) UnityEngine.Debug:LogException(Exception)

 

Without plugin list there are no ideas