^
That really wouldn’t help and I would be very careful with messing more with the cart especially with pressing it down onto the board, flexing it causing more potential damage.
The fact the game is running means his cart and SIMMS are likely fine. otherwise it would even get into the attract mode.
This is likely a problem with the PPU, it will need to be verified and reflowed, or possibly replaced with one from a donor board. @cruzlink2 has repaired a lot of these boards with the same issues. I highly recommend his services.