I need some help please. Have just restored a White Water. Everything has been working fine. After a few days I suddenly had the issue that mid-game Big Foots head started spinning endlessly and as soon as the ball went into the boulder garden the machine decided that it had been tilted! Odd behaviour. Have been into the menu and the big foot opto 1 shows as not working in the test. Took the big foot opto board out, all looked OK, but not working. Bizarrely when the playfield went back down with a bit of a clunk, miraculously the opto was found again and Big Foot played nicely for a few minutes until yet again mid game, he started to spin endlessly and the game tilted! Someone might see the connection between all of this! Maybe its not that opto, but something else playing havoc? What do you guys think? Any help appreciated.

Which test should I run to see if any of the other switches are the problem?

Thanks both LTG and SnowYeti for your suggestions. As it turned out, it was a diode on a totally different switch in the same matrix. The switch on the main ramp behind big foot had been squashed down touching the connection on the switch and caused every other switch to become flaky including the bumpers, tilt, slingshot. Never would have thought to check another diode and would have kept focusing on what appeared to be a failed Opto. Took 5 minutes to fix once you guys had made suggestions. Many thanks again. Mat