I was in a hotel parking and went to right little room with stairs to undeground. Also, 2 zombies were running after me, so, i went from outside into this room and closed the door. And for some reasons those zombies weren’t trying to break the door but they attacked near walls (my character heard THUMP sound). So, i tried to go underground, and suddenly i found that zombie are going after me too. How the hell they went inside? The door wasn’t broken.
It’s a bug, it’s a goddamn annoying bug. I don’t know if it’s known or not though.
This bug was around for so long I bet it’s known.
Yeah, this is a good known example of how the current multi-z-level building system sucks. 
Are you sure they were attacking the walls? I’m pretty sure doors make the same sounds if they fail to damage them (and since doors are pretty strong it can take a fair bit of zombie power to bust them down).
I passed few turns (~7-9, can’t say exactly) in order to be sure they’re attacking walls, not the door, so yeah. Maybe i should check myself one more time.
I reproduced it. Not “THUMP”, but “WHUMP” sounds as like they attack door. But even so there were 150 turns and this door still isn’t broken.
That’s just an ordinary door and it was attacked by ordinary zombie. Either doors were upped or zombie obtained lesser bashforce.
It was a bit of both and happened when zombies were given the ability to pile together to help break doors. As a result a single zombie will find it almost impossible to break through a door (which isn’t that crazy, a door without any windows would be extremely difficult to break into just by hitting it with your hands when you assume the most difficult case, which is a door that opens towards the breaker). A group of zombies will all work together though and stack their strength, and should be able to break through a door with a fair bit more ease.
Well, although that’s realistic, that also make the game easier.