[L473ncy]

That's impossible the motor only turns the gears to pull the spring back. No matter what the motor will spin the gears until the last tooth of the sector gear when it will then release the spring/piston to push air out the barrel. Either the motor will pull your spring or it won't (or struggle with pulling it but still able to pull it), there's no "half pulling". It's totally discrete, either it does or doesn't.

You probably have other problems like the main spring is worn out or that the piston o ring isn't sealing or something. I don't know what it is but it's not related to the motor.