Passing through seemingly solid patches

[sweet235]

This bug has been known for some time. Recently, we found a way to reproduce it on an open source map: https://github.com/Masmblr/map-staratcs_src

A dretch can pass through this wall, where this screenshot is aiming at:

I inspected the map source and found noting suspicious. The map was built from commit 4e1501a.

This particular instance was discovered because a bot fell down to the bottom of the surrounding box, and the game would not end without admin intervention.