Well, I received the returned motor today. The buyer claimed that the shaft was "wobbley" whatever that means. So first I checked it with a dial gauge and it showed it was true. Then I mounted an APC 7x4 prop and ran the motor up to 12,600 rpm. No vibration or shaking of any kind. Here's a photo of my test. I believe the buyer didn't know what they were buying and changed his mind when it arrived. So I deducted from the refund the price of the Priority Mail to send it to him, the price of the box, and the price of the MO. If he complains, tough.