+1
Happens all the time for me, have had stuff disappear entirely on sketchy ground (raised floor, slopes) as well.

@TeeTrizZz

Did find the option now. Feeling a bit silly, gonna be more thorough before reporting next time.

<thinking aloud>
AFAIR zombies get less server cycles than players, also they don't supplement their collision detection from a "clientside", so (just guessing) if they have a motion vector and intersect a collidable while "between cycles" they can clip through.

How about making zombies slow down again at building entrances? By that I mean, only at doorways/steps/stairs. It would make buildings useful again to lose zombies but still prevent people from looting at the same time as the zeds could still run inside.

Might solve a few of the glitching issues.