@TeeCee I was having connection issues between my RC and S9+ phone. As you also use a Samsung it may be a similar cause. After several months of a solid connections it started regularly losing connection mid flight between DJIGo4 (v4.2.16 )on the phone to RC. Initially it was ever few flights it happened, then it became most flights. Very annoying.
I think I have fixed it, but I cannot be too sure just yet. Have had about 10 fault free flights. I went about troubleshooting it somewhat methodically to try and establish the cause.
Things I tried with NO improvement
- Placed phone into flight mode to disable wifi and phone. Unlikley to fix as it was a USB issue but seemed worth a try.
- Cleaned USB connectors on phone and RC
- Tried three different types of USB leads all with different configurations.
----Side of RC to USB-C in Phone.
----Side of RC to mini to a USB-C adaptor then to USB-C in Phone.
----Bottom USB on RC to USB-C in Phone.
No change here, Still got disconnects with all three leads. Furthermore in my case restarting the RC always re established the USB connection. So to me this ruled out the USB leads or connection point being my cause.
This left me with with the Software configuration of the phone:
Things I tried that lead to an apparent fix..
I turned developer options off.
I had four flying apps on my phone. DJIGo4, Litchi, Drone Deploy and Drone Harmony.
I uninstalled Drone Deploy and Drone Harmony
I disabled battery optimization for DJIGo4.
Since doing this I have not had a disconnect.
So try removing any other flying apps you may have installed and try disabling battery optimization for DJIGo4.
To disable battery optimization for DJIGo4 on andoid
Go to Android Settings > Apps > Special Access > Optimize Batter usage > All Apps. the scroll the list to find DJIGo4 and make sure it is unchecked.
I am not sure yet what seems to have fixed mine but something in my phones software configuration changed by removing the apps or changing the battery management and now it looks like it is fixed.
good Luck..