My MiSTer seems to have a sync issue going on via YPbPr. Not sure what's causing it exactly, but I only started experiencing this within the last few days or so. Experienced this with the GBA core's start screen, with Rusty on the ao486 core (running at 15khz), and with Mega Man 2 in the NES core. It causes the top of the screen, or the top of certain images to be distorted over to the left, and I'm not sure why.
This does not happen on original hardware, as this video I recorded demonstrates (look at the top-right corner in particular). So, that tells me I need to change a setting on my MiSTer. But I'm not sure what exactly would fix this. Does anyone know?
(I already tried flicking the sync-on-green switch, but that made it worse, so that's not related to my issue. I also didn't have this problem the first time I loaded up Rusty, but when I tried it again a couple days later, that's when this issue started happening)
(first pic is of the GBA core's start-up screen. Second and third pics are from Rusty in the ao486 core; third pic is especially bad because the art causes the girl's hair to distort, and point toward the left of the screen)