Hello. Thanks for playing!
It isn’t a bug, but intentional that those side rooms are sealed off, because they aren't needed anyway if the player doesn't have the crown. The catacombs aren’t important either. I’m aware some players still might look for the catacombs key, even though it’s not to be found. So I have to do something about that.
You should however, be able to escape the dungeon via the stairs without collecting the crown, because the entrance by default always is open.
Just out of curiosity. How many endings have you achieved?