I would start by redoing the connectors throughout the game. The input to the 12v is fine.
At minimum I would repin the connector J3 on the solenoid driver, J4 on the mpu and all 3 on the rectifier if they haven't been done. This will get you started but usually is it best to do all of the connectors on the mpu.
Report back after repining those and we will see what issues if any remain.