The metal studs on the unit should hit the switches when it has all the bonus counted up or all counted down.
It won't count down if the switch is open and vise versa.
Check your switches.Make sure they close and contact.Count up manually and it should stop at the switch and at the open space.The opening is the max the wheel will turn.It should go down from there.
It's possible you have the studs on the wrong side of the switches

You can also check the tension on spring.

Nomally is should step up and down smoothly with about 4 turns of the spring.

Too loose or too tight, it won't step one way.

So if the mech. steps smoothly both directions. Then here are the switches you can check for scoring the bonus.

The Green will start the sequence
The Blue will keep the count going down until the bonus reaches zero.
The Red is the switch on the stepper. (The white pin is keeping it open in your picture)

FYI - After the bonus is scored the stepper should step up one step.

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