getting this in console -  

[ZoneManager] UpdateBehaviour is null. Report this on uMod 

(Filename: ./Runtime/Export/Debug/Debug.bindings.h Line: 35)

Are you running a command that triggers the error?

Not at all the server is empty and I observed it watching the webconsole

The error "ZoneManager] UpdateBehaviour is null" occurs when a player connects to the server.

Failed to call hook 'OnPlayerConnected' on plugin 'ZoneManager v3.1.2' (NullReferenceException: Object reference not set to an instance of an object)
  at Oxide.Plugins.ZoneManager.OnPlayerConnected (BasePlayer player) [0x00000] in <e089463a2eb94dd6a4e236a868109faa>:0 
  at Oxide.Plugins.ZoneManager.DirectCallHook (System.String name, System.Object& ret, System.Object[] args) [0x005f8] in <e089463a2eb94dd6a4e236a868109faa>:0 
  at Oxide.Plugins.CSharpPlugin.InvokeMethod (Oxide.Core.Plugins.HookMethod method, System.Object[] args) [0x00079] in <23ba99f131254889867c71f0bd137b1d>:0 
  at Oxide.Core.Plugins.CSPlugin.OnCallHook (System.String name, System.Object[] args) [0x000d8] in <157a94ee66ab4a7991faecd1eb84be3b>:0 
  at Oxide.Core.Plugins.Plugin.CallHook (System.String hook, System.Object[] args) [0x00060] in <157a94ee66ab4a7991faecd1eb84be3b>:0