[Bug] Unit capture: Imps fail to pick up KO enemies (bodies shift across ground)

From Steam topic: https://steamcommunity.com/linkfilter/?url=https://brightrockgames.userecho.com/

Reprod steps:
1) Campaign map: 7 - Heart attack
2) I built 2 chokepoints with Guardposts, bombards and lotus blade trap
3) I waited for assault to start
4) I built first prison 4x4
5) Prison was filled up
6) I built second prison 5x5
7) Imps trying to pick up Dwarves and bodies are relocating themselves
8) I sold second prison
9) I removed prisoners from first prison
(At this point imps successfully started bringing prisoners to first prison)