Was going to make a more organized video but every time I tried to do something, another new thing went wrong so here is a 5 minute video showing the main issue and some timestamps to jump to listed below.
https://drive.google.com/file/d/1gabT0QUWTy5U09V3DyJ9DH26No0nyj6j/view?usp=sharing
0:00 At the start, I have set up a course on the GPS, and I am following it. No wind and balanced weight to make things easier. importantly, the HDG switch is OFF.
0:08 As I adjust the CDI to the left or right slightly, you can see the plane turn in that direction. I then let it re-align with the course.
1:55 Then I adjust the roll command knob several clicks to the left and it works as expected.
2:21 Now, messing with the CDI doesn't cause the plane to try and follow the new course. Good.
2:28 Then I turn the roll command knob two or three clicks back toward center (but still very much left of center) and the plane banks HARD right. Despite, as you can see in the video, the yoke still being turned to the left, as expected. At this point, it's clear the plane is following the NAV course while the yoke is correctly obeying the roll command.
2:38 Shortly after this I turn the knob further left and the plane banks left again and seems to be obeying the roll command as well, though I'm not sure if that is a direct result of me turning the knob again.
3:35 Then I try to re-center the roll knob, and the hard bank happens again. The plane turns and slowly levels out at seemingly a random heading (not the HDG bug or the CDI, not even a direction which would indicate an attempt to capture the course).
4:28 Another attempt to get the roll command to work, resulting in a hard bank yet again. If you notice here, the yoke is almost full left, but the ailerons are neutral.