HoT / ToV
 

Mobs ignore walls, path straight through them / fall through the world. They will cut/phase through walls instead of going through the hallways.

This is a video of HoT but this is an issue throughout ToV.

Mobs have even become permanently stuck in the walls in certain spots of WTOV.

https://www.youtube.com/watch?v=6eKx0qhsqvQ