I came here to post the question as to why my doors seem to disappear from my dungeon after some time. Initially I noticed it was always wooden doors, but then occasionally with braced doors too. I thought maybe it was a 'feature' of sorts where wooden doors could rot after a certain amount of time, but it seemed inconsistent.
After searching this forum, I saw a post about training room doors taking damage. Is this so, and is it intentional?
Edit: I just re-added a wooden door to my training room there to see it first hand. A Giant was training and then out of nowhere, he walked over to the door, hit it, it broke, then he walked back to where he was to resume his training. Do creatures destroy doors out of spite? That's hilarious.