Orcs moving away & despawning after being attacked

My town was sealed off from the outside world. When I remove the door to let invaders in, the orcs (4) spot this opportunity and attack. While moving in they are attacked by veranuses. They flee, move away and despawn.

Steps to reproduce:

  1. Load the save
  2. Remove the door in the blue circle

Expected Results:
The orcs flee back to their camp or move in to attack.
Actual Results:
They flee the veranuses, move away & despawn after having followed one of the red paths.

Version Number and Mods in use:
Alpha 20, release 701 x64

save.zip (8.5 MB)