This unit is mislabeled as a Professional model. We have the replaced the worm follower gear twice. The replacements last about 2 1/2 years. My wife uses our mixer a lot and it seems the worm follower gear is designed as a wear item. The rest of the mixer parts are fine. The repair is straightforward but very messy due to the grease. Get all of the old grease out (removes any stray metal shavings) and put new goop in. This time the gear cover was going on too tight after the repair. Used some washers to keep it from overtightening which would have seized the motor shaft. Expect to be doing this again in 2+ more years. I ordered 3 gears this time. Most important tool to have is snap (retaining) ring pliers.