WPT ace in the hole issue.

It sounds like a vibration issue to me. When you stick your finger on the lock pins, you're kind of holding the whole ace in the hole unit still. It stabilizes the thing and prevents it from shaking as much. Have you inspected the opto wiring for that area to make sure it's sturdy?

Alright, but you're still holding the unit steady. It's switch 59, which is an opto, that triggers ace in the hole. If the opto switch is triggering, it means the beam is getting interrupted somehow. It could be the transmitter side stops lining up perfectly with the receiver side. It could be a wire isn't making good contact with one side, so it's not powered. Whatever is causing it, the light is not getting from side A to B. You need to pull your playfield up and look at those two opto boards, and make sure they're screwed in nice and tight and that the wiring is well soldered to the board.

Edit: I say soldered, but they're weird boards and I don't have a WPT in front of me. They may be plugs. Either way, the wires need to be making good contact.

Pinball Center has one, but it's $$$$.