I have a 2015 Cherokee without dual climate, just regular manual controls and I can't get any air out of the defrost vents. Last year I moved it from floor to defrost about 10 times and it started working again, This year that didn't work and cold weather will be coming.

Hot and cold works fine. Front vents work and it will move to floor vents but nothing comes out of the defrost when switched to it, It keeps coming out the floor.
All the videos I see only mention older models or the blend door which does the hot/cold, but that works fine on mine.

I took the radio trim off and I see the motor moving some white gears on the drivers side, sometimes it stops, sometimes it sort of bounces. I assume some gear is stripped but I see no way of getting to this motor.
Do I need to have the entire HVAC replaced?

Thanks.