My Craftsman garage door opener would open about a foot and then immediately reverse itself. It would do the same kind of thing when I tried to close it. When I took the cover off, the problem disappeared. Putting the cover back on brought the problem back again. So now I've been leaving the cover off, and there are no problems. Does anyone know what's going on? I would like to be able to cover the motor and circuit board, to keep out dirt and junk. Thanks a lot in advance!