Hello,
We've been having a recurring issue with our M600 where it will default itself back into ATTI mode shortly after take off on each flight.  When it's sitting still on the ground, it will remain in GPS mode with no alerts or issues.  After take off around 75ft it will bounce back in to ATTI mode and begin drifting.  If I fly it in DJI GO, I can see the mode flick back and forth between GPS and ATTI mode.  I initially thought it was related to Ground Station Pro or the remote, but I'm not so sure any more.  Ive got a help ticket in at DJI, but they only move so fast...  I'm thinking it could be a loose connection somewhere or a bug in the firmware?  Does anyone have any ideas or experience with a similar issue?  

I have only had the same situation happen to me due to lack of GPS signal strength.