I m experiencing the same issue since long time ago... (the screen comes black and says disconnected...) , even at short range flights and even with different phones / usb cables. I ve noticed that
1) I can control the drone, it's just a problem of the "app"/camera view
2) This problem may happen either minutes after take off or when it is landed before taking off, indifferently and randomly.
3) I tried to move the cable... never disconnected while moving it...
4) tried different firmwares in the drone (P3A), different versions of the DJI app, on different phones (samsung s4 "was the worst", samsung s3-neo, meizu
m2 note mini)..pretty the same unpredictable issue.
5) After disconnect, after a 30-60secs of terror, the video signal USUALLY auto-reconnect, or, I can detach and re-attach the cable to make the app reconnect to the video/data signal (dangerous!!!)..
6) Soon after the connection is lost , having the latest versions of the app installed, make the drone come to the base quickly... of course you can stop the going home procedure when the signal is back.
6) It feels unsafe to fly long distance away having this issue, so I am very disappointed and thinking about to contact dji support...
7) With my previous drone (P2V+) I never experienced those disconnection and felt much safer...