We are sorry to hear about your incident. Map Pilot is not actually flying your aircraft. The app loads waypoints into the aircraft and they are executed by the aircraft's firmware. Once the RTH is initiated there is nothing that Map Pilot could do to cause what you saw.
Map Pilot does not fly your aircraft at any time. It is loading waypoints into the aircraft which the aircraft then uses it's internal control to fly. It sounds like their may be some sort of hardware failure or something like that that caused it to leave the programmed flight mode which it uses to fly the waypoints. Once it is out of that mode it is no longer under waypoint or Map Pilot control. If you attempted a Return to Home button push and it didn't respond there was almost certainly some sort of hardware issue going on.
DJI Go needs to be fully closed. Running DJI Go in the background, that is not what FULLY CLOSED means. We always say not to fly with any other drone applications running. If you don't do the home button double click and swipe up to fully close DJI Go that means it was still running and is almost certainly the cause of the issue. Trying to keep DJI Go open for logging purposes will cause more problems than it will ever solve.
The log file is weird though because usually we see a transition to ATTI mode when something makes the aircraft leave the programmed flight mode. In this case the data just stopped. It is odd that you were able to watch it go since usually when this happens it is due to some kind of hardware failure which causes the trad
You can view the Log Files using AirData to see if there was anything interesting in there but in the case of hardware failures the telemetry usually stops being transmitted from the aircraft.
Again, we are sorry you had a problem and without the aircraft you may never be able to figure out what actually went wrong but based on the information you have provided I would say that there was a GPS or IMU failure.
PS - We replied to your initial inquiry via email about an hour after it was received. Please check to make sure that our email address is whitelisted with your email server and check your spam filter.