This intervention army has been basically sitting there for 10+ turns next to the town and not attacking. Originally it was not exposed but 6-8 turns ago I used some heroes to expose it as skaven town. Still it doesn't attack. Didn't attack when enemy army was there for a bit, doesn't attack when it's empty. Ran away once and attacked and razed another town and came back and doesn't attack.
Save game file is attached.