I went flying yesterday and had the Phantom in GPS Mode. It acquired all satellites but it did not maintain position, it kept flying in a 20 foot radius around me which seemed to progressively get worse. I switched to Atti mode and it stopped at least flying in circles. I upgraded to the new 3.16 Naza software which requires you to also update the controller as well before I took it out. I don't know if that is related or not.