-I made a script and placed a lot of bunnies then i placed some walls to prevent them from escaping.
-I noticed that some of bunnies was ghosting trough a walls.
You may also try to set a walls in editor then place soldiers inside place where is no way to escape, then give them orders to move out to specific location, sometimes they would ghost trough walls.
Sometimes your AI buddy will ghost trough fences if you give him order to move out or to follow you.