The console is a PS1 PAL (is modded, not sure if it has an impact) and I’m using the 240p test suite from github, the latest build.
The shimmering issue is pretty weird because it always happens on the same vertical lines of pixels. It’s as if some vertical lines where changing size while scrolling horizontally. Again, it always happens at the same spot no matter where this spot is on the screen (so it affects always the same left portion of a cloud for instance). The higher the scrolling speed, the less noticeable it is. It’s the same no matter the settings I use (and I purposefully messed up the settings to try to figure out where it comes from)
It really feels like the background is (let’s say) 319.5 pixels wide and screen is 320 pixels, so it’s like certain rows of pixels can’t remain stable. And it happens no matter which mode I’m using.