(20:59:49) | [Oxide] 20:59 [Error] Failed to call hook 'OnEntityTakeDamage' on plugin 'ZoneManager v3.0.2' (NullReferenceException: Object reference not set to an instance of an object)
  at Oxide.Plugins.ZoneManager.HasEntityFlag (BaseEntity baseEntity, Oxide.Plugins.ZoneManager+ZoneFlags flag) [0x0000e] in <675e44b6dc44475a8d38137e3621f5dd>:0 
  at Oxide.Plugins.ZoneManager.OnEntityTakeDamage (BaseCombatEntity entity, HitInfo hitinfo) [0x001b1] in <675e44b6dc44475a8d38137e3621f5dd>:0 
  at Oxide.Plugins.ZoneManager.DirectCallHook (System.String name, System.Object& ret, System.Object[] args) [0x003dd] in <675e44b6dc44475a8d38137e3621f5dd>:0 
  at Oxide.Plugins.CSharpPlugin.InvokeMethod (Oxide.Core.Plugins.HookMethod method, System.Object[] args) [0x00079] in <9affce1cd15c4ec183941adef8db1722>:0 
  at Oxide.Core.Plugins.CSPlugin.OnCallHook (System.String name, System.Object[] args) [0x000d8] in <4452f821def6406d834e4149849fe7ea>:0 
  at Oxide.Core.Plugins.Plugin.CallHook (System.String hook, System.Object[] args) [0x00060] in <4452f821def6406d834e4149849fe7ea>:0

 

This was what 3.0.3 was supposed to fix, so you may need to update.