Savefile attached as I can't determine why this happens.

I have 4 working square keys in my inventory, and one broken one. For some reason, 'o'pening the door yields the message that I don't have a key in working order, which obviously is not correct. The door can be opened by 'U'sing an intact key. For some reason the game only checks that a key is broken, but doesn't go on checking for other keys. I don't know toe B/U/C status of the keys, but perhaps the key check goes in sequence blessed-uncursed-cursed (as the game never offers cursed keys to be used when you have others available), and then stops after the blessed (broken) one?

Dropping the broken key also stops this behaviour.