One of errors was caused by autolights

(Filename: <5af03239cf5a4d58bd6e55cdcd64ce09> Line: 0)

NullReferenceException: Object reference not set to an instance of an object

  at Oxide.Plugins.ZoneManager+Zone.CheckLights () [0x00016] in <5af03239cf5a4d58bd6e55cdcd64ce09>:0 

  at InvokeHandlerBase`1[T].DoTick () [0x000be] in :0 

  at InvokeHandlerBase`1[T].LateUpdate () [0x0000c] in :0 

And another is caused by a collider check

(Filename: <5af03239cf5a4d58bd6e55cdcd64ce09> Line: 0)

NullReferenceException: Object reference not set to an instance of an object

  at Oxide.Plugins.ZoneManager+Zone.OnTriggerExit (UnityEngine.Collider col) [0x000a6] in <5af03239cf5a4d58bd6e55cdcd64ce09>:0 

There also apears to be an error when calling hook 'Unload' on plugin 'ZoneManager v3.0.91' (NullReferenceException: )

It's this bit of code here that is the problem in InitializeCollider() -

                    if (sphereCollider == null)
                    {
                        sphereCollider = gameObject.AddComponent<SphereCollider>();
                        sphereCollider.isTrigger = true;
                    }
                    sphereCollider.radius = definition.Radius;
                    bounds = sphereCollider.bounds;
                    collider = sphereCollider;
​

- also occasionally getting the Unload() NRE.