I have a problem with opto 2 in the trough. I found it not working, so I cleaned it, put in place and now in test all works fine. But during gameplay something is wrong with Kahn multiball: sometimes only 2 balls are thrown in mb, instead of 3. This happens only if there is no ball in the Sanctum. If one ball is in the Sanctum, then that ball is released and one launched by the autoshooter (plus the one already in play): so it's ok, 3 balls mb. But if there are no balls in the Sactum, then 2 should be launched by the autoshooter. And here is the problem: only one is launched. When this happens, it's enough to nudge a bit the machine, and immediately the third ball of the multiball is launched too. I think when I nudge the machine, the opto in the trough works fine and detect the correct number of balls.
But as I said during test all optos work fine. The issue should be related to the opto, but what to check now?