i'd love to get the answer to that too, because i hate on some servers zombies just teleport [ or glitch ] through door, walls, floors.... Or open the door or just walk through the door frame as if there was no door at all.... Another issue is ladders or high points like roofs and somehow the zombie is able to get up to that point. Some terrain passibility check / pathing behavior (as stated by Reggie) server side would rock to fix it...

... Special Note to the Mod Creators
, I totally am OK if a Zed can break through a light door such as an interior hollow wood door, a screen door, a weathered glass sliding door, glass windows, etc and maybe keep the persistant damage if the structures are repairable [and I would love to see both player built and Map Gen structures be upgradable though that might be a post for another Mod or such... not sure who might want to look ino that suff!

Thanks for a Great Mod and keep up the awesome updating!