What happens when you touch their back? I assume the door does not move very fast, if it does it's not a safe door. When my door is opening in the morning they squat down to go out while it's still opening. Mine is totally safe as it is hanging from a string so it can't put any down pressure.
The best thing to do is watch their behavior and habits and make absolutely sure the door does not close before dusk (not sundown).
JT