I bought a really clean white spark fly more combo used for $450 with 4 batteries and the American flag wrap. The spark looks great, flies great but I noticed later that one motor without the prop on when you spin it by hand sounds not as quiet as the other three motors. I also noticed that the top of the motor shaft was slightly bent. I used a house key and ever so slightly bent the shaft back. I have compared it to other new sparks, and there always seems to be one louder motor. My motor however is still louder than the new spark, but it is not rough feeling or difficult to turn. If you spin up the props then shut them down, the noisy motor stops spinning right inline with the other 3. My thought was a noisy bearing. Maybe this spark got dropped onto the table or ? and bent the shaft and damaged a bearing. I see no signs of a crash on the spark. The noisy motor never feels more warm than the others after flying. I have flown it many times and keeping a watch on it but trying to decide to order a new motor for $30 and put it on or let it ride. This spark does have dji care on it but not in my name. I emailed DJI support to see if it can be transferred to my name.