Servo Gear Teeth
A maintenance issue that I have had with the MSR has been with a stuck aileron servo that made it tricky to control.
A friend found the problem for me using high magnification with a digital camera. There appeared to be plastic swarf stuck in one tooth of the larger gear. Since my problem occured at the time of purchase I believe it was a defect with the original sero.
The servo only seemed to hit this point close to the limit of full left stick. It would hold at this point. Until more left stick was applied it would not come free.
I ended up replacing the whole servo and the problem disappeared .... and Yes I probably could have simply pully off the gear tooth and replaced that rather than going to the trouble of pulling the entire servo off the 5in1 unit. However, that idea came to me afterwards!!!