Unless things have changed, a single tile in front of a door has a tendency to attract building destroyer who then get stuck by the incredible gravitation of the destructible object, being unable to walk away (sometimes not even juicy prey to squish was enough). I've actually had that problem where the BD came in diagonally from the side, ended up just in front of the door, and then being unable to back out one tile (perfectly pathable) to destroy the door (this was on a device with a door in each end of a corridor with repeating menacing spikes in between. There were also raising drawbridges outside the doors). This was all on 0.40.19+, though.
Come to think of it, I've lost a bunch of guard dogs in 0.42.01-02 where a stair led up to a door with a the dog inside and a grate as the floor (looking down on the ground above an entrance). Invader trolls kept smashing the locked door and the grate. I also had a strange issue with a titan who got locked up, allowing the caravan to get both in and out, but the trade liaison thought it was a good idea to first leave to the east and then decide to leave mid south instead, so the titan got lose and killed the thick skulled liaison (the skull was thick enough to let the caravan leave before he died...). The titan then returned to the dog house, and I unlocked the door in the mean time, which allowed the titan to destroy the door and the grate and then chase the dog.