I noticed a bug today that causes Players and Crawler zombies to clip through the ramps on military towers. when a Player/Crawler begins to turn the first corner on the tower they proceed to clip under the ramp onto the ground, or get stuck in position. This bug is present is all official maps containing these towers.
The same Collison issue is also present with some of the metal nodes within Keryev (Russia), allowing Crawlers and maybe Players to clip through at the right angle.