@0dan0, reporting a new issue. I'd describe what I'm seeing as a intermittent "wobble" where vertical lines from subsequent frames are not consistently straight/vertical.
I'm currently running firmware 7.7.1 on a modified C scanner (8mm film with a 12mm lens).
Investigation so far makes me feel that it might be an artifact of the shutter speed setting, or some other Auto-Exposure related control. With the scanner set to Auto Exposure mode, I notice the wobble when the source image is inherently bright, which sets the ISO to a low value (50). However, when the image is very dark, and the Auto exposure adjusts a higher ISO (100, 200, 400) the wobble generally does NOT appear.
I have some further video that demonsrates what the on-screen display displays when the wobble happens, and when it doesn't. I'll share it with you if you like.
If it sounds like I'm on the right track, and if you have time, perhaps you could provide a test-build where a minimum ISO can be set, or a similar setting for the shutter (max speed or min speed). That could help validate what I'm seeing with bright footage.
As an alternative, I may purchase a lighting gel (netural density) and stack it on the LED light plate (under the film) to cut the brightness of the backlight illumination, which could force the ISO/Shutter into a range that doesn't result in wobble artifacts.
Thanks!