Just after Christmas I crashed my P3A and sent it to DJI for repair.  Damaged gimbal, legs, compass ribbon cable, parts of the upper shell popped over the bottom shell.
Before I sent it in, I was weighing my options to get parts and fix it myself, replace with refurb, or have DJI fix it.  While I was weighing my options I noticed one motor didn't sound as smooth as the others when spun by hand and you could hear a bit of play if you rocked the motor side to side against the shaft in the right angle.   I don't know if it was like that before the big crash.
I opted to have it repaired by DJI who practically gave me a new drone: new body, legs, gimbal though for the gimbal they quoted/charged me for a repair of the gimbal.
They apparently didn't notice the slight play.
This evening I noticed the play might be getting a bit worse but drone otherwise flies OK.   I know you all are going to chime in and say replace that motor before it fails and crashes which I am inclined to agree.  I'd send it back and have the pros replace the motor since it is a pain to open the case but I'd hate to have to wait another 3 week turnaround time.
I can definitely replace the motor myself though I dread the pain of opening up the case, and not torquing the screws just right on account of the cracks that tend to develop, not to mention it was just repaired.

I'm just wondering though if anyone else noticed a slight difference in spin noise on any of their motors compared to the others and how long have you run it with the difference in the sound?

Hello, IMHO. You should replace the motor. Side play + noise = bearing failure or bent shaft. The motor still runs but is near a catastrophic failure probably in flight when loaded. To open the shell is not so difficult. You just need a few old credit cards and patience. The motor cables are soldered to the center board. The AC  will be in serious problems  if the magnets touch the stator. Please don't take the risk. I had one motor that sounded different to the other 3. I applied a single drop of oil to each bearing and the noise disappeared. My motor has no play at all. Hope this helps.

I'm planning on replacing the motor, but seeing if DJI will send me one since they forgot to include props in the repair quote which were sent and obviously damaged but said they'd send me one.
Definitely sounds/feels like a bearing problem.
I've taken the AC apart before having sent it in for repair.   Probably what made it harder to get apart at the time was because the plastic at the seams were out of place.

DanMan32 Posted at 2017-1-26 17:50
I'm planning on replacing the motor, but seeing if DJI will send me one since they forgot to include props in the repair quote which were sent and obviously damaged but said they'd send me one.
Definitely sounds/feels like a bearing problem.
I've taken the AC apart before having sent it in for repair.   Probably what made it harder to get apart at the time was because the plastic at the seams were out of place.

I think you made the right decision. I forgot to mention that  you should be careful when tightening up the motor screws. The infamous cracks begin there. Just to avoid this, I bought a torque screwdriver to apply the right amount of torque to these screws. There available used on eBay. I got one for less than $30.00. It was used to tighten screws and bolts on human prosthesis and implants. I had to send a disclaimer to the seller since this tool can no longer be used on humans or animals. I simply calibrate the tool to 2 oz-in to tighten all motor screws.

It sounds like you just snug them.
I'm only replacing one motor so I don't need to touch the other motor screws.  The screws holding the arms together is another matter.