Looks like you need to adjust your motor height. What I do which is quite different than what most do, is tighten the little allen bolt on the bottom of the handgrip until it stops (motor all the way up) then back it off one full rotation and fire the gun on semi. Back it off another half turn, if it gets quieter then back it off another half turn, if it gets louder turn it back to where it was before when it was quieter.
I find from the position of being all the way in the motor has to be dropped 1-2 full rotations of the allen on average. Chances are if there was a burning smell then the motor was too far in and was being jammed against the bevel gear, adding a whole lot of resistance and making the motor work more than its designed for.