Fine tuning the small potentiometer has definitely helped a bit with the text stability, but doesn’t stop the jittering, jumping, or artifacts. Detuning it far clockwise causes the overlay to prefer it’s rightmost position and also become warped a bit.
I actually found a magical fix to all the issues, which I’ll have to keep working with this week to make sure it’s stable, but maybe you can tell me why this works. If I put a 10 microF capacitor connecting pins 8 and 9 on your shield, all the jittering goes away and the overlay displays correctly on the video. (another maybe interesting fact: the overlay also displays correctly in “sync mode,” but without the video of course)
I’m pretty new at this and have trouble trusting my diagnosis, but this seems to be a board issue, or maybe a power source issue possibly. The capacitor bypassing the UNO seems to filter out whatever voltage fluctuation was being problematic.
Maybe you can tell me a better way of doing this filtering if the bypass capacitor is a bad practice or something.