Quoted from vireland:
It sounds like the wire to the opto has broken, at least partially, inside the insulation and is making intermittent contact. This is not unusual for Stern optos. Try wiggling the wires to the opto while in switch test to see if it triggers them.
Thanks. I’ll check that out. Is there a way to get power to the playfield without sticking some tape to the button inside the cabinet? This is my first stern so I’m getting a crash course on all of their quirks and ways to do things....