Just a little point in the right direction please.
On occasions my flippers don't work when I start a game. Sometimes they do, sometimes they don't.
I've tested them in switch tests and they activate and beep as they should. I also gave the optos a really good clean with some IPA not that long ago which removed a lot of dust and dirt.
What else should I be looking for? A mate has suggested replacing the U20 chip I think he said???