So I have had the phantom for about a month now and fly just about every day. Getting ramped up for a trip to Aruba (taking the phantom) and expect to encounter wind and wanted to get some practice in ATTI mode so I studied up and turned on Naza-M mode today for the first time... Most of my flights have been around the neighborhood as was the first flight in Naza mode.. Everything went well. It was cool being able to turn off the GPS and have it drift with the wind. It was also nice to see the extra "attitude" it has in ATTI mode... EXTREMELY NOTICEABLE!! After the test flight me and Fam decided to go for a walk at a local path that has a old historic train trestle(converted into part of the walking path) that goes over a huge river and I decided to take the phantom. Took it out and started getting some cool shots and within 2 or 3 minutes the thing started pulling away from me, HARD and uncontrolled!!! It was "steering" into some higher trees so I ramped up the gas to ascend and luckily it responded to that and started ascending but still pulling away HARRRRDDDDD despite NO directional input!! After It cleared the trees and they (the trees) were no longer a problem I reached down and flicked the switch into ATTI mode and THANK GOD it stopped pulling away. I got my bearings on the FPV and brought her back closer. I flew the rest of the battery much closer and as I flew I noticed a HUGE ISSUE... The day was clear.. we were over a wide open river but the GPS seemed to have a serious flaw... Before takeoff I let it lock on to 9 GPS'.. While in flight it would bounce betwen 13 / 12 AND........ 0 Thats right in the wide open it would lose ALL GPS signals (according to mini iosd).. 10 or so seconds later.. BOOM... 12/13 locked in again.. Then a few seconds later, same general area... 0 . The remainder of the flight the behavior continued. I decided to test another battery and the erratic GPS behavior continued that entire flight also.... As I monitored the GPS problem I would immediately pull it into ATTI mode as soon as the satellites dropped so no more "fly-away" behavior but still very unnerving!! SO... Is there a GPS bug in Naza-M mode??? This issue has NEVER HAPPENED in the month that I have had the phantom and I fly almost daily. I know that there was/is a theory the Naza-M and flyaways were linked and from my perspective this seems SPOT ON. Luckily I was able to save mine but definitely scary!!!