The big mixer has always been very noisy but yesterday it was very unhappy indeed and made a loud noise and then ceased to turn right in the midst of bread making. I had seen a post about cleaning and re-greasing your mixer but this one is new and also a different model. A quick Goggle search turned up this excellent video on repairing a KitchenAid 600 Pro that isn’t spinning, exactly my problem. Jason had to help me get some of the parts off because my hands just weren’t strong enough but we succeeded in the end and diagnosed the problem as teeth broken off the worm follower gear. I’ve ordered the part and now we wait. I spent $5 on the part and we needed special pliers that were $14 as well as some grease to re-pack the gear box. I suspect it’ll be much faster and cheaper than sending it back to the factory which is the only other option.