Hi, I just got a Phantom 2 vision and I noticed it is drifting to one direction in flight if i put the sticks at center. It doesn't always go in the same direction. Compass was calibrated and GPS signal is good - lights are green before takeoff. Switches S1 and S2 are in the up position. This has caused me to panic maneuver away from trees and crash a couple times. Any advice given on how to fly or best mode of operation would be greatly appreciated.