So, when I have it running, there can be a loud rattle. It sounds like it's maybe metal peices not fitting togeather exactly right and the vibrations are rattling them against each other. If there's a little pressure put on the head to the floor, it seems to get somewhat quieter. BUT, I took the head off, and tried to turn the motor manually and there is a spot where the motor gets tight. But once it's running and I power it down, the motor quietly, smoothly, and slowly winds down. Can anyone help me with this?