if the game doesn't see a ball in the shooter lane it will continue ejecting balls from the trough until it sees it. It sounds like you've spent a lot of the time looking locally in the trough/shooter lane area. Have you looked at the CPU board where all those wires go? Maybe reseat the associated connector or re-pin if this ever had battery alkaline corrosion or is otherwise corroded. I would go into switch test and drop a ball in the shooter lane to make sure it sees a ball.

Did you have a credit dot for that switch or did you finger each switch in test to find it?

So really it’s not just sending 2 it’s trying to eject all of the balls out of the trough? If all the switches work normally in switch test, I’m leaning towards an MPU issue at this point. It’s an expensive troubleshooting measure, but it may be time to swap out the MPU.

Thanks for coming back and telling us the fix. Many find the fix and don’t report back.