The server console is getting these errors like every 2 minutes. Also if you are in the flags menu, you get spammed/flooded with these messages. It will flood the console and drop the server fps down to 2.

(Filename: <1238ece1b72a4758add65c4eb185f601> Line: 0)

NullReferenceException: Object reference not set to an instance of an object
at Oxide.Plugins.ZoneManager+Zone.OnTriggerEnter (UnityEngine.Collider col) [0x0008d] in <1238ece1b72a4758add65c4eb185f601>:0