This update with the explanations is pretty okay, but the fact that I've zero immunity frames when entering, making me lose a heart without being able to avoid it, is still annoying. Many times I've lost a heart due to this alone. Give me immunity frames when I enter a room.
Edit: 
Please fix the intrinsic issue, having a double-door for no reason other than to stop backtracking (which you can just do by sealing off all other doors permanently when you choose one) rather than attempting to fix it with programmery. A fix of the initial problem is always a better fix than the fix of the symptom.