So I tried multiple times to capture a good example of the problem. The video captures look pointless so I’m not going to bother showing it. The best I was able to capture can be seen with thist link: https://imgshare.io/image/20201015-2120081.NxfSiO
This is the File Select screen from Mario Party 3 which has a dark blue background and is a worst case scenario. You can clearly see the diagnal lines in the blue shade. Now try to image that they are moving as well. The direction and speed can change over time.
I suppose the pictures of the second link are closest. Though it seems to effect the entire screen there. On my end it’s only certain large shades of color.
The S-Video cable I use has proper shielding and most definitly uses a 750hm resistor as there is no brightness issue. I’m unsure if the capcitors are necessary. I’ll see if I can open the AV plug and check what components they added. Maybe that is to blame here. Still think its weird that the Retrotink MINI’s auto comb filter completely solves the problem though.