It seems like every company I have worked for has issues with their computer system when there is an upgrade. When I worked at Comcast, our system would be down hard for hours after an upgrade! But, after a week or so, the system was not only back up and running, but better than before the upgrade.
I have the Galaxy S6 Edge. I always clear all apps before I fly. I also have ALOT of memory available in my phone. That being said, I have noticed if I get a phone call while flying, and then ignore the call, the app quits. I then use the hard return to home app on the remote. Then restart my phone. Is it frustrating? yes, a little. But its more routine now. I think a lot about work-arounds, just like I did when I worked at Comcast.
You'll also find that about 20% of the MavicPro drones have issues, obvious ones, right out of the box. My third one is a charm. But, not after returning two of them and getting a nasty gram from Amazon saying that they may have to cancel my account if I returned any more stuff. My sense of humanity and the A to Z promise just sends my brain off into orbit when I see things like that! But, it would be worse to have purchased it from DJI. They expect you to keep the defective drone until they come up with a fix. Did I mention they don't understand English very well? Big Box stores now charge a re-stocking fee for returning the Mavic. Apparently they've had a few returns!
But, I can tell you I was in the same exact boat you are after my first drone failure of all sensors and the Mavic being stuck in ATTI mode. I had to reset my expectations by doing the following.
1) The Mavic Pro Drone is the best bang for the buck out there. PERIOD
2) DJI is a Chinese company, with Chinese customer service. Expect to repeat everything you say, even when in Email form! They are the worst to deal with when things go wrong.
I hope that helps.