
So I guess this might be the problem? How can I fix this?
sorry, I don't know. you have different board version, so I can't help you. you should take a photo of socket with removed CPU, and also from the underside of board.
IIRC, that last pin on CPU was connected to ROM, so it gave black screen on boot with broken trace, consult the schematics.
you can fix broken traces by using a wire to 'bridge' them, but be extra careful not to connect wrong points..