The same thing just happened to me with my spark also. Was at a state park getting some footage. Out of nowhere it switched to att mode and started saying compass error and took off full speed which said I had a speed of 56 mph. For some reason it did not record home point so when the
battery started getting low it just landed. Last glimpse I got was of it landing by a fence 12000 feet away from my location. I used find a drone searched for 4 hours and trust me it was no where even close to the coords it said. Dji would not cover it for a fly away. It's my 3rd spark now with almost everything for it. At the end of my rope with dji on this.