UPDATE: I reproduced the bug on multiple locations, and screenshots.
Version: e1.0.11 (newest beta up to date)
Settlement name: Multiple
Media:
drive.google.com
I was able to place troops anywhere inside or outside of the castle (in battle area).
Troops inside didnt seem to attack properly the enemy, instead jamming up against the walls trying to get out, or even jump from walls.
I have a
saved game file of the siege, when leading the attack you can
always repeat the bug.