In the video, it looks to me like the part of the drive pawl that is currently riding the gear teeth is not the correct part of the pawl. The actual part of the drive pawl that is supposed to ride the teeth is below the cut-back section of the pawl. The cut-back section of the pawl is only there so that the pawl can be retracted by the subtract arm on steppers that reset, such as the one you are working on.

This mis-alignment of the drive pawl in relation to the gear usually happens when the metal spider attached to the rivet/wiper side of the stepper has gotten loose, allowing the gear and shaft assembly to slide away from the drive side of the baseplate. Try retracting the drive pawl with your finger so it is totally clear of the gear, and then see if you can push the gear down closer to the baseplate. If that fixes the problem, you'll need to adjust the position of the spider on the other side of the baseplate and tighten down its two set-screws to re-attach the spider firmly to the gear shaft. While you don't want the gear to be able to move away from the drive side of the base plate, you do need to leave a tiny bit of end-play between the gear shaft and the bearing so that the gear and spider don't bind against the bearing when the gear rotates.

- TimMe