Zombies phase through the doors of 'land_guardhouse' building, the do this weird animation, kind of like stepping over something and just phase through it.
I'm yet to see this happen on other doors, it happened on Chernogorsk, in front of the fire station, they seem to only phase when aggroed. I was playing official, LA server, chernaurus.
I guess after so much time they asked, zombies are finally going through doors.