After sieging Ubersrike the besieging army gets stuck in the river just below the bridge. Happened to my army which forced a reload of save.

Now I see it has happened to AI army, size of about 50.

As of now, there are 10 armies who have been trying to attack them for a long time. Abandoning all defenses of other towns and they do not attack anything else either.

This 50 army is hogging armies around 1500 total, which has an impact on the war effort.