Mori55 said:Did you crash it ? Flying sand , dirt ? May need a new motor.
Panamon Creel said:Screws that are too long or a screw forced too deep can cause damage to the motor winding. Bearing damage, dirt,...etc. can be detected by turning the motor by hand looking for abnormal noise and resistance. Also look for a missing c-clip of the motor shaft. A faulty ESC can also cause the type of issues you are describing.