My Phantom will not hover when flying in GPS. It flies slowly backwards and slightly increases it's speed. I see this on take off as the Phantom will almost jump backward on liftoff. I have to keep the joystick forward and a little left to hover or just to go forward in a straight line. All LED lights indicate everything is fine. All the props are fine and they are balanced. This occurrs on no-wind fly days at very low altitude; 10'-15'. I tried flying in ALTI and the same thing happens. Anyone have any thoughts? Thanks.