The red bonus arrow should switch sides for every ball played, unless you get an extra ball and Same Player Shoots Again is lit. Think it should be LRLRL for 5 ball games. The two lights at the top kickout hole should switch from left to right every time the ball hits the rubber up there hard enough. Perhaps a blown bulb or bad socket?
You're right, Grand Prix is a GREAT game! Got mine in the beginning of March and absolutely love it.