Sorry for the delay, if I don't respond to a thread it isn't on my subscriptions and I miss notifications. Typically a chatter has too possible causes the brakes are loose or worn or the voltage is too low. If the brakes work properly they must both be present, they should come out and stop when the blades are turned in one direction with the magnet held steady and then retract when twisted the other way. If you twist past the stop point they will come out all the way and the shaft will come off. It is possible for the brakes to be worn and fall out easily, be missing or for the cogs they engage on on the magnet to be worn to the point that the impeller and shaft can turn without being engaged on the magnet.
In a low voltage situation (below about 112V) the pump will struggle to start, the impeller blades are now 1.7mm smaller to drop this start voltage to about 108V. I see you have the older full size impeller which I personally prefer, you get better performance. If you have low power in your area or brown outs or your house is just maxed out from AC running all the time in a heat wave, you may need the smaller impeller.
The defective motors were from early 2007 they form a bulge in the center rotor room, usually the impeller gets locked in or has a lot of friction when being removed.
I apologize for the 6101, the earlier motors had some electrical problems and could short out because the board overheated inside and cracked. They cool and work but stop as soon as they heat up again.
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