If just some games are show this problem then it is some sort of software problem.
If you have some cheats installed or some other homebrew with overlays etc, then it might be causing these issues.
If all games (and the home menu have the same problem then it's a hardware problem.
The first thing I would check is the flat cable that connects the LCD with the motherboard.
It might be that it partially slipped out of the socket.
Another possibilities are that the cable is damaged, the connector is broken or the connections have some corrosion.