How about replacing the ram modules? Most modern computers that don’t have dedicated video cards use main ram for video. Bad ram bad image quality. Most desktop computers have all the ram n dual inline memory modules. If you have two you can take one out and move the other to a different slot. Take one out, test replace one with the other, test replace both with brand new, etc
Somewhere along the way RAM modules often became soldered on the motherboard, in a bid to cut the cost of manufacturing.
OP is disabled, so the option to check for that possibility is reduced.
In any case, it is certainly a possibility but I haven't seen bad RAM modules in years.
Insufficient RAM, certainly. But not bad RAM.