I had/have some problems with my FC40 not behaving as expected. It had a problem rotating left spontaneously in hover but that seems to have disappeared after loading the defaults file (twice) and full sets of calibrations. What still remains it something that might or might not be classified as 'operating within normal parameters'. Since I've had it we've had a fair bit of wind here. Nothing the Phantom can't handle but it limits the circumstances in which I have been able to observe its flight characteristics. I also have only one Phantom and cannot compare it with another one. What happens is that when I am hovering in GPS mode and just give left stick yaw input the Phantom doesn't hold position but begins to drift pretty hard. Just as fast as it does in ATTI mode it seems but not in the same straight downwind direction. I'm not yet sure whether it behaves 'symmetrically' and its deviation is the same when rotating left as it is when rotating right. An asymmetrical behaviour would indicate something most likely not being as it should be but symmetrical behaviour might be within the norm. Now I have read about people experiencing changed, less stable hovering behaviour after a firmware upgrade from version 4.00 to 4.02. Mine has the latest. I now wonder whethet it might behave differently if I would downgrade to v4.00. Its behaviour could be described to look like this if it is indeed symmetrical. The two tracks do appear to be at a 90 degree angle from each other. After releasing the left stick it returns to its original hover position from where it started its track. My question is whether this happens to other Phantoms too when rotating? And have people experienced a change in behaviour as a result from firmware update(s)? I'm not certain my Phantom behaves symmetrically when turning left and right. When I fly forward with moderate speed in GPS mode away from me and make a left turn into a 45 degree wind I see it moving left from the straight line it was on immediately. When I then let it fly towards me and make a right turn with the wind coming from the rear right (135 degrees) it rotates right but doesn't move from the straight line towards me. I have yet to do a test with the wind at 90 degrees both ways. Weather isn't very cooperative today but I hope I'll get the chance to test this today. I would also very much like to do some tests in zero wind but that's not going to happen any time soon according to the weather forecast.