Sometimes these Bally steppers have a subtle mechanical issue with the alignment of the drive arm and the anti-back-turn ratchet that causes a problem similar to yours.

To check for this, try unplugging the game, and operating the stepper by hand. First reset the stepper, then very slowly operate the drive arm (especially as the plunger comes out of the coil on the return stroke) to step the unit up from 1 to 2. Watch the action of the ratchet and drive arm as you do this. Then very slowly operate the drive arm again to step from 2 to 3. If the stepper arms have a mechanical adjustment issue, you'll see the same glitch that you show in your videos.

- TimMe