It seems to vary from server to server and/or session to session. Sometimes it will work correctly and zombies cannot run through doors, other times it will be reversed (they can run through when it is closed but there is an invisible barrier when it is open), and sometimes they can run through no matter what. It's especially annoying as these zombies run very fast and seem to never stop chasing you...at least they don't ruin all your gear in one punch anymore though.

May just be bad luck for me but it has happened on every server that I have been on. I must say though I do like the new Zombie model where there are only a few Zombies until you make a loud noise (I.e. fire a shot) then a hoard of Zombies attack you.

Its the same for me that it warys. It never works in the supermarket in electro

The AI reads the status of the door inverted, if you open all the doors of a house the infected wont enter, but if you close one, it will enter through that.

Yeah, Came back to this game after giving it a bit of a break and was wanting to see the progress, but I see that the progress seems to be going backwards, So far after playing for 5 hours they do run threw doors, The server of curse restarted without warning, I joined another server and had to wait the 60+ sec because I guess I server hopped from a server that restarted with no prior warnings (Typical), Zombies were running threw the doors that were closed when I spawn in.

I ended up joining a different server later on due to Desync and had to run from a zombie, after he tired out I ran pretty far ahead of him and he was able to walk threw the door the closed 30 sec or so ahead of him.

How is this broken again?

Just found Duplicate thread (25547), Devs. are aware of fault and it is Scheduled for a fix.