My Phantom 4 using the DJI GO 4 app, the image keeps lagging.
iPhone 6 Plus.
On my brother's iPhone 6 Plus and my dad's iphone X it doesn't do that.

Is your firmware up to date? I found the last update fixed this for me.  (iPhone 6s)

My firmware is up to date.

Please see this thread , i have the same issue with ipad mini 4.
It apparently depends what kind of chip is the device . You need at least an a8x chip. I even have a8 and you can see my example clip , has got the same you have.
I bought now ipad pro 10.5 and hope to test this coming

https://forum.dji.com/thread-133969-1-1.html

You say firmware is up to date, is the RC at V1.9.3 ?

This can be checked by looking at 'About' in 'General Settings' menu.

Aardvark Posted at 2018-2-8 13:35
You say firmware is up to date, is the RC at V1.9.3 ?

This can be checked by looking at 'About' in 'General Settings' menu.

It is: RC at 1.9.3, drone at 02.00.0700

gmota_23 Posted at 2018-2-10 05:37
It is: RC at 1.9.3, drone at 02.00.0700

Try deleting and reinstalling DJI Go 4 on your iPhone 6 plus.

And the firmware on your phone at latest iOS 11.2.5 ?

I've read in the past where a backup and recovery of device using iTunes has helped, whether that points to some anomaly in iOS I do not know. But if all else fails may be worth considering.

My Phantom 4 using the DJI GO 4 app on my ipad, when I am at 1500 meters the image hangs and the signal loss message appears. This message appears in open areas and without interference from magnetic fields. Can someone help ?!
Thank you!

Rafa-Rebelo Posted at 2018-2-11 17:38
My Phantom 4 using the DJI GO 4 app on my ipad, when I am at 1500 meters the image hangs and the signal loss message appears. This message appears in open areas and without interference from magnetic fields. Can someone help ?!
Thank you!

I had the same problem of video transmission issues with the RC firmware version 1.9.3.  I was advised to resort back to a previous version of this firmware.  Loaded 1.8 and the problem was resolved.  All of this with the latest AC firmware installed.

Hope this helps

fans02010415 Posted at 2018-2-16 12:57
I had the same problem of video transmission issues with the RC firmware version 1.9.3.  I was advised to resort back to a previous version of this firmware.  Loaded 1.8 and the problem was resolved.  All of this with the latest AC firmware installed.

Hope this helps

How did you downgrade rc firmware to 1.8.0? When I select 1.8.0 and do a firmware refresh it does not stick. After restarting the rc it shows I still am on 1.9.3...Thanks!

You might have to reload the DJI Go 4 app  and then revert back to the RC firmware version 1.8

You may want to delete the app from your phone turn the phone off .Turn phone on and reinstall the app. It worked for me. Good luck.