Quoted from Wickerman2:
How about this one: The "hit" lights on the Roto-Target--there are 3 of them that light when you hit one of the 3 exposed roto-targets? My left light wants to light up...no scoring issues, doesn't affect gameplay, if you give the machine a nudge, it comes on/off but likes to stay on. There's a Left Roto Target light relay which I cleaned/adjusted and looks good but still have the issue. If you nudge/lift playfield it affects it so seems like a switch gap issue somewhere but only spot I see on schematic that affects that light is the AA relay.
I have been following this thread, used to own a 'Super Spin' so quite familiar with Jet Spin. I would check out the contacts on the roto-target. When the ball hits, it knocks the switches backwards and changes the gap (often ending up too close) Kind of a design flaw on roto-targets IMO. REgap the targets a bit wide and see if that clears it up.