I have a friend with a Phantom4 and a Mavic Pro. He controls both a/c with his iPhone and DJI GO4.
Everything works as it should with the Mavic, but he has all kinds of problems with the video feed for the Phantom4. His next test will be to put his phone in "airplane" mode and see what happens.
Any thoughts or suggestions will be appreciated.
Thanks.

He should make sure all background apps are closed.  Also force kill GO4 and restart it.  I've had this problem on my P4 and this fixed it.  Using IOS. (also have a Mavic)

Looks like the persons who work as programmers at DJI botched the latest firmware on Phantom. Just take a look at all the threads on this forum. Mavic uses newer technology, possibly better designed from ground up.

Hummingbird.UAV Posted at 2017-7-25 13:38
He should make sure all background apps are closed.  Also force kill GO4 and restart it.  I've had this problem on my P4 and this fixed it.  Using IOS. (also have a Mavic)

Thanks for the info. I forwarded it on...

Alxy Posted at 2017-7-25 13:46
Looks like the persons who work as programmers at DJI botched the latest firmware on Phantom. Just take a look at all the threads on this forum. Mavic uses newer technology, possibly better designed from ground up.

Mavic uses totally different hardware to transmit the video signal.  You cannot change P4 hardware into Mavic hardware via programing.

Mavic and Phantom 4 have different hardware as well as the performance. For the video feed issue of Phantom 4, please check the image transmission settings whether the channel is stable or not. Change to another place, cable or mobile will be helpful to verify.