Units keep on attacking wall even though the target behind the wall is destroyed

[This game is laggy]

Here's a video showing this bug: https://www.youtube.com/watch?v=8SMUJP6RogI

After the garrison is destroyed, the heavy cavalries still attack the wall. You can see that there's no more favored target behind the wall as they turn back to attack the mill after the wall is destroyed.

Incidentally this video also demonstrates 2 other bugs

• at the beginning, cavalries - both the attackers and the defender - attack each other from a distance even though they are melee units.
• after destroying the wall (~0:23), one of the cavalries moves all the way to the far side of the mill before attacking instead of attacking from the closest side like the other cavalry