The Ladies First Chicken Door opener has a safety stop built in so if your chicken is hanging out under the door it won't get crushed. It won't even break an egg. Check out the video here. Sometimes coop debris can accumulate in the doorway or something can fall in the way such as a branch. When it stops it will not be able to get pushed up any further because the screw has to be turned by the motor for the door to open or close.