Got an issue with my guardians last week which I want to share with you. Maybe someone can use this info in the future.
When shooting the ball in the scoop (upgrade / mode select / mystery / extra ball) the lit function(s) rarely gets activated but the ball will get kicked out. I'd had to shoot the scoop for like 4+ times to get to another mode. And sometimes it would just register immediately.
But the ball always got kicked out, no ball searches occured.
So I ruled out the switch at first because the ball gets kicked out every time. Replaced the SD card with the original one thinking maybe there's a corruption on the card but that did not seem to be the issue. Checked all the settings in the menu but there was no improvement there.
Got into the switch test and found that the switch was registering but it was intermittend. Meaning: when the ball enters the scoop the switch would register like 4 to 5 times on and off fast and would stay activated after that.
Checked the switch and found that one of the screws was missing and it was tilted into an awkward position and causing the described issue. The screw was found lying inside the cabinet so that was quickly fixed.