Was out flying today and was live streaming to facebook. While streaming, I switched to photo mode. This cut off the stream to facebook (which makes sense in hindsight), but it also froze the app. I shut the app down and restarted it.. and it just said DISCONNECTED and wouldn't regain the feed from the camera. I tried disconnecting/reconnecting the cable and no change. Had to RTH blind, which thankfully worked great.

Try uninstalling the app then reinstall it back make sure firmware is updated via dji go or dji assistant 2

Hi there, may I know which drone and which mobile device you are using? For this case, please help to confirm if it is the RC signal disconnected to the drone or RC disconnects the DJI GO 4 app. If you are able to control the drone at that time, it might relate to the app or mobile device, so please try to reinstall the latest app ( remember to back up the files and sync the records) or change another mobile device.
If it is the RC signal disconnect, please try this way: on a flight, please take off and hover nearby for while, then flying after receiving a good signal. See if it helps.

DJI Thor Posted at 2018-3-15 20:29
Hi there, may I know which drone and which mobile device you are using? For this case, please help to confirm if it is the RC signal disconnected to the drone or RC disconnects the DJI GO 4 app. If you are able to control the drone at that time, it might relate to the app or mobile device, so please try to reinstall the latest app ( remember to back up the files and sync the records) or change another mobile device.
If it is the RC signal disconnect, please try this way: on a flight, please take off and hover nearby for while, then flying after receiving a good signal. See if it helps.

DJI Mavic Air
iPhone 7
Go4 with all updates to software and hardware.

RC signal to the drone never dropped, as best I could tell. It came home when RTH'd.