I've got a weird thing that keeps happening randomly the drone will be up in the air and then I'll loose all connection in the app on iphone7+ dji go4 app. The screeen says disconected so I loose the video feed & all data. However the controller is still connected & I can still fly & land the drone.

Sometimes it comes back if I quite the app & re-open a few times. It seems to be completely random. I can't work it out.

Anyone else had anything similar? I've updated to the latest firmware & it doesn't happen as much but still happens..

I had issues connecting with the app with a Galaxy S7, it turned out to be dirt in my USB port, the cable wasn't fitting properly. You should try another cable and clean your lightning port.

Dirty data port is not the usual cause of this problem.

You have 2 choices:

1) Fly on the original, short usb cable provided by DJI with phone IN AIRPLANE MODE,
2) Use a third party cable connected to the bottom port of RC without the need to have the phone in Airplane mode.

Have you tried to use the original lightning cable to connect your phone to controller?

Yes I have exactly the same problem and so do lots of others with the iPhone 7 Plus. As has been said using airplane mode or using the other USB port on controller will solve your issue. But its not a real fix id like to be able to use the normal cable and still leave my phone not on airplane mode so I have data.

I will have a try again but I couldn't get the full size USB port to do anything with my original apple lighting cable. I reinstalled the firmware & that seems to have fixed it a bit.

I have similar issue with my Mavic. I'm using Galaxy S7 Edge with Android 7.0
Drone is loosing video stream randomly and sometimes when it happens the DJI Go 4 app crashes and I need to open it again. Mavic is not loosing connection between RC and drone is fully operatioal. I just don't see what is going on in the air.
It doesn't matter what is the actual distance.

Other issue but I'm not sure if it is related to connection problem is that the gimbal freaks out sometimes and is tilting all directions becoming out of focus for couple of seconds and Recording stops. I cannot operate the gimbal at this time it happen.

I did re-calibrate all sensors, format sd card, re-linked Remote conntroler, switched to another phone (Galaxy S6 edge Android 6.0) and try 3 different USB cables but did not fix the problem. All firmware is up to date.

I attached some samples related to my issue with video feed.
(best seen from 0:50 sec to 1:20 sec)
https://drive.google.com/open?id=0B5drVtx0gXuEQWtZWm8taG10anM
https://drive.google.com/open?id=0B5drVtx0gXuEUEJ1cE1GdUFrak0
https://drive.google.com/open?id=0B5drVtx0gXuEQktBeFRiWnUzdFk

Any ideas?

Putting the phone into airplane mode seems to fix it on mine. Although I do still restart the app sometimes.