The FAA and NTSB can't catch everything. sadly, new rules will apply after an accident. it was obvious in the 727 that crashed. the stew used the normal stair release and nothing happened. they discovered she didn't know about the emergency handle and nobody realized the normal stair control door would hide the function when left open. they can suggest, recommend and force rules. it depends on the problem.
They suggested having the door swing the opposite direction, never happened. proper training about the functions, probably was done. and better placards with better instructions. not sure if that happened either.