My s8+ has disconnected most flights.This "trick" works with Mavic Pro.
1. Start app only , enter camera view and scroll around the map. This is to get the surroundings, quite helpful during flight. Once you have the area map in your Go app, the next flights in the same area will not require this step. I think Litchi does not save offline maps as DJI Go does, if you consider buying Litchi. But the disconnection issues will be just the same
2. Put mobile in airplane mode. Leave location on. Also wifi on should not interfere. The main thing is that you are not connected to the network/mobile operator.
3. Do a normal connection/startup sequence and you should be ok hopefully.
4. When finished flying do not forget to put the phone back in normal mode (airplane mode off) so you can get callsI do this before even turning remote off.
I suspect the cable connection into the phone.
Wouldn't do the first upgrade but did the recent evidence after 3 starts...