I bought a coop from Horizon Structures that had an automatic chicken door installed. It seemed to be functioning perfectly but now I notice that the door is not shutting all the way at night. It goes down but leaves about 1-2" gap at the bottom. I can push it down the remainder of the way, but that kind of defeats the purpose of an automatic door, doesn't it? Any ideas on what could be causing it to do this and how I could fix it?