I had an issue a few weeks ago whereby as I hit the retract landing gear button I watched the LED colour of the drone go from purple to orange. It had been hovering just fine, holding position prior to hitting the retract button. Figuring it had lost GPS for some reason and I was now flying entirely manually, something I've practiced, I got straight on the controls, but it wouldn't respond. With no obvious change in wind, the drone suddenly veered off and crashed. The shell was cracked and 4 props broken. Checking the logs when I got home I could see the drone seemed to think it's altitude had plummeted to negative height, presumably thinking it had dropped below ground level. But nothing else obvious. Figuring this couldn't be user error I contact Yuneec customer service who quickly replied and arranged for the whole kit to be returned. Two weeks later and brand new drone and kit has been delivered with a fault report for the old one saying it had a GPS sensor problem. So I'm very grateful for the superb, prompt customer service in dealing with the issue and getting a replacement drone out to me. Also reassuring in some regards that it was a fault and not operator error. But I'll be doing a lot of testing in wide open space to make sure this one is OK. From what I've hard DJI aren't quite so good at offering support in these instances.