Always make sure that GO is the only running application ! and turn off WiFi. If you use such as Litchi always ensure you kill the application before opening Go and the same in reverse. Its simple double click the home button and swipe to remove the application.
The GO application is designed to be the "sole' running application and has some strange issues when other apps are running. Obviously DJI cant fix these as they will never have a mix of applications running on their development tools.
So do exactly the same....