I began to play and when I hit a bonus target (Red or White, lit or not) the Yellow Bonus Relay comes in (Print Location F-14)and the Yellow Bonus Unit Step-up Solenoid (Print Location F-28) fires but the advance of the stepper is immediately retarded because the Yellow Bonus Zero Solenoid was also fired (Print Location F-6) allowing the Yellow Bonus Unit Step-up Solenoid Reset (Print Location E-35) coil to fire. It will do this for both first (Yellow) and second (Green) players.
Also, sometimes when scoring bonus of a red or white target or every time when draining the ball, the ball count will begin to advance a random number of times.
I could really use some help trying to understand the normal operation of the Yellow/Green Bonus Zero Solenoids and how they are possibly tied into the Drain or tabulation circuit. - Tom