Re-visited. Now i totally agree with you. The Infirmary door locks when it re-shuts, and locks from both sides. So wow, if you unlock that door, do not go in with the key, and do not go in without it. Ha! Whoever opens this door needs to stay on the outside and let others go in.
The fix would be: once the door is opened with the key, the lock does not reset, or the door does not auto-re-shut.
I got this all hosed up and the only way was to find another player who had a set of these keys. And that player was....Sam! lol thanks Sam!