Yup i got your problem.
What happens, is the little screw that you are turning to adjust the motor height, isn't tight enough in it's casing
every time the motor turns, instead of staying still and holding the motor in its proper place, it spins with the motor, and makes it go higher and higher until it can not turn any more.
I highly suggest getting a new pistol grip and motor plate.
This will fix your issue once you properly adjust it.