This is the error message I get when I encounter the problem in the actual project. Still digging!
MissingReferenceException: The object of type 'PlayMakerFSM' has been destroyed but you are still trying to access it.
Your script should either check if it is null or you should not destroy the object.
HutongGames.PlayMaker.Fsm.SendEventToFsmOnGameObject (UnityEngine.GameObject gameObject, System.String fsmName, HutongGames.PlayMaker.FsmEvent fsmEvent)
HutongGames.PlayMaker.Fsm.Event (HutongGames.PlayMaker.FsmEventTarget eventTarget, HutongGames.PlayMaker.FsmEvent fsmEvent)
HutongGames.PlayMaker.Actions.SendEvent.OnEnter () (at Assets/PlayMaker/Actions/SendEvent.cs:39)
HutongGames.PlayMaker.FsmState.OnEnter ()
HutongGames.PlayMaker.Fsm.EnterState (HutongGames.PlayMaker.FsmState state)
HutongGames.PlayMaker.Fsm.SwitchState (HutongGames.PlayMaker.FsmState toState)
HutongGames.PlayMaker.Fsm.DoTransition (HutongGames.PlayMaker.FsmTransition transition, Boolean isGlobal)
HutongGames.PlayMaker.Fsm.ChangeState (HutongGames.PlayMaker.FsmEvent fsmEvent)
HutongGames.PlayMaker.Fsm.Event (HutongGames.PlayMaker.FsmEventTarget eventTarget, HutongGames.PlayMaker.FsmEvent fsmEvent)
HutongGames.PlayMaker.Fsm.Event (HutongGames.PlayMaker.FsmEvent fsmEvent)
HutongGames.PlayMaker.Actions.TriggerEvent.DoTriggerEnter (UnityEngine.Collider other) (at Assets/PlayMaker/Actions/TriggerEvent.cs:38)
HutongGames.PlayMaker.Fsm.OnTriggerEnter (UnityEngine.Collider other)
PlayMakerFSM.OnTriggerEnter (UnityEngine.Collider other)