I have four of these motor's on my QX350 and two of them are very noisey. The bearings are not smooth. It causes vibration which affects the video quality.

I have the same problem! Two motors are running rough and I estimate that I only have an hour total flying time on them! The video has gone to jello. The two that run rough also run very hot and would burn you to touch them after a flight. Can they be rebuilt? At $50.00 each they aren't much of a bargain either! I did find that the multi star replacements from HK are junk and not worth
messing with them! Two out of the box were junk right from new! One had debris drpopping out! So is there a
better motor available at say half the cost? I'm reluctant to buy more blade motors only to find the same poor quality again.