I have not flown the x5c extensively. so I can not comment. Intuitively I believe that the single motor/blade assembly, that spins easily, would perform differently than the rest. Gear mesh seems good on all, no foreign material present at top or bottom. The prop screws are equally tight. Will 'ground effect' cause instability in hover? I have not flown this more than 40cm above the floor.
Purchased new less than a week ago. Amazon. The somewhat limited instructions imply that 1 M is the minimum flying altitude. I am reluctant to fly it outdoors because it ran away from home the first time...