That's normal. It's supposed to be like that.

Steppers with two solenoids can step both forwards and backwards and usually have some kind of mechanism to keep them from stepping out of the range they should step through. The missing teeth on your stepper gear is a mechanical way to prevent a stepper from advancing too far. Other steppers use limit switches which offer an electrical way to prevent stepping too far.

If your stepper can take only five steps after resetting it could be used for the ball count which in many games shouldn't go past five steps. You can make out the missing teeth in the video at:

https://www.funwithpinball.com/exhibits/small-boards#BallCountUnit

and see that if the stepper were to take a 6th step the wipers would reach places that aren't wired.

/Mark

Unless you're sure you know what you're doing, I wouldn't recommend that.
This forum is full of posts from people who tried shotgun cleaning & adjustments, and caused more problems than they were originally trying to solve.
What to do instead: Slowly and carefully diagnose one problem at a time and then fix only that.
http://www.pinrepair.com/em/index2.htm#clean