My 1.1.1 has about 50 flights on it give or take. Maybe a little less. About 10 flights ago I started noticing what I call a resonation vibration in flight only. It started out small and barely noticeable and has progressed to a startling, jello producing vibration. Up front, I will say I'm kind of a fanatic about things like this. Some would surely ignore what I consider a serious vibration. I took the propellers off and CAREFULLY examined them one by one for cracks, nicks, warping, threaded collar damage etc and can find absolutely nothing. They look brand new. No crashes ever. Prop guards have been installed since the first flight. The vibration is so bad now (IMO) that after the last flight, I've decided to ground it until I find a cause. On the ground if I hold the Phantom down and run it up full throttle I cannot detect a "serious" vibration. In fact, the only evidence I have is from my camera video. I can hear the resonance in the props when watching the video and I started getting Jello in my videos about 10 flights ago. Also, when hovering around a low altitude it seems ok. It only does it after it's been up like 50 feet or more for several minutes...worse if there's some wind. The vibration seems to be worse towards the end of the flights. Not so much at first. This is leaning towards a motor(s) heat issue. As if a motor is getting hot and the bearings are acting up once hot. Maybe from a lack of lubrication. The motors are relatively new (young) so you wouldn't expect the motors to be failing...but new Chinese parts are not immune to failure. I removed the props and ran the motors up full speed...one feels very smooth, the other three have a very slight vibration. Nothing bad and possibly normal UNLESS the motors should be "sewing machine" smooth. Not sure about that. 3 of them have VERY slight vibration but the shafts have no play in them left, right, up or down and spinning them by hand revels no rough spots or any other noticeable problems that might indicate a magnet coming loose etc. I would kinda relate this to front wheel bearing vibration on a car. If you've ever changed front wheel bearings on a car you can probably appreciate what I'm talking about. It seems to be that kind of a vibration / resonance. All motors are securely fastened and there is no movement whatsoever. There is absolutely no melting or distortion of the shell and no cracks are present anywhere. I have ordered a precision balancing rod to check the balance of the propellers but the props all look perfect and they are clean. For all intents and purposes, they look "out of the package" new. So to be honest, I'm expecting to find them all well balanced. If they are, I think I'll go ahead and replace the motors. For $40, it's probably not worth waiting for one to fail. Since I may be replacing them anyway, I did order some of that teflon lubricant to try. Nothing to lose and if it resolves the issue even temporarily, I'll know for sure it's the bearings. Could an ESC controller board cause his? I don't see how.