Hi, can you upload a video of this bug to
upload.taleworlds.com? Please paste the link to this thread in the description box on the upload website so I can identify it.
I think i recognize the behavior described in point 1 here.
It is somewhat hard to reproduce on demand as it requires an opponent with a relatively specific troop composition and a specific set of orders issues by said opponent (Essentially the enemy AI has to cooperate). That said, under the correct circumstances this is easily and consistently reproducible:
1. Ensure your party has a large amount of archers in a group. More archers is better for demonstrations sake (50-75 or so works wonders).
2. Ensure that the archers have the order "Face Enemy" for their position. Also, ordering them in "Loose" formation makes the issue more noticeable.
3. Ensure the opposing force has some horse archers in it.
In this configuration the archers try to maintain their line by rotating around a central point. This means that the archer in the dead center does not have to move except for rotating around on his own axis. The archers on the outer edges of the line will potentially have to run around a lot to get to their new spot on the line if it needs a strong adjustment.
This mostly happens if the enemy makes a relatively small charge of horse archers. The horse archer AI will circle the unmounted archers. In response the archers will - if they lock onto a horse - try to rotate their entire line as a group in an attempt to face in the direction of the fast-moving horse archer. In line formations this leads to a massive amount of movement on the edges as the on the edge have a LONG way to run to a new spot every time. During this time they won't shoot, and this can - in extreme cases - lead to the entire formation being rotated when the enemy infantry closes in. (Eg: Facing backwards or sideways relative to those)
This behavior can also be reproduced somewhat without enemy AI cooperation. When attacking an enemy while having an overwhelming force, the enemy AI will hold position and defend. If in this situation the player rides to the enemy on horseback one will notice that their entire formation turns around to face the player (Albeit them generally being in square formation, which means less extreme movement than a line formation). Even so a formation can be "Tricked" into rotation 180 degrees this way, which exposes them to archery fire from the main force (Or at times, even a cavalry or infantry charge they don't react to in time).
Note the latter strategy is just an example of formation turning (The result is much more extreme in a line formation of archers that attempts to rotate to target a horse archer).