The Comfort Zone CZ442 will produce a loud screeching noise if the motor is jolted out of alignment. Left in this state, the motor may eventually burn out completely. This guide covers the realignment of the motor.
Press the safety switch briefly to confirm that the motor can spin. Slightly tighten the screws and adjust the motor's alignment by hand until it can spin freely. A light rattling or noise is fine and will be fixed later.
Keep your fingers clear of the motor while it is spinning.