Plot hole: Amy lets Scully place the witch in the break-room, but how could she have known that after captain Holt steals the crown out of the locker, he would go there? And not for example goes back through the window he came from.
Other mistake: Holt takes the crown out of the back of Jake's cabinet. However this wouldn't be possible as the crown was in the top drawer. This would have a back on it and it wouldn't be accessible by just removing the back of the cabinet.