There is a cutout switch that turns off the fan when the cover is closed.
That switch goes bad sometimes.
It may or may not have something to do with your problem.
It is a pin that gets pressed down by the cover when it is lowered. Fairly easy to bypass temporarily for testing purposes.
But tbh your description sounds more like an overload issue with the lift motor. Have you tried to grease the lift assembly? Or maybe something has become unaligned, a screw turned loose or something, and now the motor does not have enough power after the first turns? If that is the reason, and you crank it up further manually, I would expect the motor to not be able to crank it down either.
