Quoted from flipperdoktor:the bonus reset relay is not triggered if the ball falls into the bonus hole or if the Firecracker bonus "Collect Bonus" is given, so the bonus unit does not step to zero ..
I don't think the Bonus Reset relay should fire in those cases, the Bonus Score relay should:
Firecracker Bonus Reset relay (resized).jpg
The left part of the schematic shows that the Bonus Reset relay only fires when the Out Hole switch or relay close and the Bonus Unit disc is between 2 and 10. That leaves the Bonus Score relay in the middle part of the schematic that should fire the Bonus Unit Reset solenoid to count down the bonus. If the Bonus Score relay doesn't fire check the switches in the right part of the schematic. I'd start with the Game Over and Tilt relay switches at the bottom since neither bonus score situation seems to work.
/Mark
