You should post this in the Slugfest club. Not really a modern game. more of an early SS.
That being said, ignore the optos as those are normally closed switches. The target switch bank has a tight cable but you can pull the whole assembly out if you remove the metal brackets on the side and carefully pull out.
The cable coming off the target bank is really tight and it travels out the access hole to the mpu. Start by looking for a loose cable on the bottom of the mpu.