1. Does it happen to all cartridge games in the same general video screen area? Or does it move or not there on some cartridge games and not others?
2. When placing in the game cartridge in and out of the slot does the video look better sometimes and not others ? If so it is the connection of the cartridge to the cartridge retaining clips (Cartridge Mount) is going bad and you will need a new one. Takes extensive De-soldering and re-soldering. Get the work done by a professional.