Quoted from LTG:The two small opto boards at the end of the ball trough. I'd remove them. Reflow the solder on the optos and the pins the connector plugs onto. And stick them back in the game.
LTG : )
This.
First stop for me when fixing two balls in the shooter lane is changing the connectors to the opto boards from IDC to Molex, or just solder the wires directly. If you’re going to solder directly, then maybe just replace the opto boards entirely while you’re at it - they’re cheap.