I also am having this issue, and have tried using a different USB-C cable, one that I use (a high speed charging cord) to charge my phone, and also a new stock replacement cord direct from DJI, and I'm still having the disconnect issues. Furthermore, not only is my phone app disconnecting, but also my RC is disconnecting from the drone, causing me to lose all control of the drone (fortunately it returns to the home point automatically). I am currently using a Samsung S9+ smartphone, and have tried uninstalling and reinstalling the DJI GO 4 app, but still to no avail. I don't recall having this problem with my older Motorola Droid Turbo phone and am wondering if it is a compatibility issue with Samsung? The strange thing is that sometimes the drone flies perfectly without any issues, and other times I get a disconnect within 2 minutes of flying. I'm so stumped by this problem.....