I guess one advantage of the backpack and taking my rotors on an off is I get an opportunity to touch and test the motors every day. Putting on the rotors today one was very stiff and did not spin normally, trying to spin by hand gave me a chunky sound an obvious resistance, possibly similar to magnet coming loose and contacting the rotor? I carefully inspected the motor for foreign materials and applied canned air just as well. A strong flashlight confirmed the lack of foreign materials inside the motor housing suggesting that the failure is either a bearing or a loose magnet. Are my only choices 3 months at DJI repair or replacing the motor myself?