For what it is worth here is what Dji told me to do to try. (reinstalling the firmware sounds impossible from the feedback I have received):
Please see below some general troubleshooting steps for 'lagging' and video issues on mobile devices:
Go to HD frequency at the top of the app.
Go to image transmission settings
And change it from Auto to custom and choose any channel from 13 to 20
If you are using a phone, turn off wifi,
also put in airplane mode. Think of any app
or hardware that may be causing interference.
Screen Recorders and other apps running at
the same time can cause this type of interference.
Uninstall and re-install the firmware update
Or finally there may be compatibility issues with the device Phantom 3 LAGGING AND No FPV
Go to HD frequency at the top of the app.
Go to image transmission settings
And change it from Auto to custom and choose any channel from 13 to 20
If you are using a phone, turn off wifi,
also put in airplane mode. Think of any app
or hardware that may be causing interference.
Screen Recorders and other apps running at
the same time can cause this type of interference.
Uninstall and re-install the firmware update
Or finally there may be Compatibility issues with
with the device the customer is using i.e. the type of settings"in the
device" or the video card in the phantom unit.
Non-visual live feed image, i.e. a blank screen that appears instead of a camera feed.
Reason: Certain chip pins on the SD card are not connecting properly tothe circuit causing the camera to start up abnormally, making the screen turn black.
Solution: Remove the SD card and re-install it tightly.
Further solution: The camera startup process is being refined to take into account possible connectivity issues with the SD card. If necessary, DJI will repair affected units as quickly as possible.
Increased lag and screen flicker.
Reason: The DJI Pilot app is extremely complex, causing it to place highdemands on your mobile device’s processor and power consumption. This is especially true of three functions.
a) Live feed, location map and Flight Route Recording all draw on processing power.
b) When activated, the Video Editor automatically transcodes your live feed and creates your video in real time using your phone’s processor
c) When the remote controller is connected to an iOS device, your iOS device will specifically use a Central Processing Unit (CPU) core to deal with data authentication computation.
All of these functions increase the power consumption of your mobile device, in turn causing its temperature to increase. Most devices will lower processing speed when a temperature threshold is reached, slowing down the app causing lag and flicker.
Suggested solution:
a) Activate hardware decoding on your mobile device in the DJI Pilot app to reduce demands on your mobile device’s CPU.
b) Choose a lower code rate under Image Transmission Quality as smaller files decode more efficiently.
c) Shut down any unused application programs, or activate “Flight Mode”
d) Keep your mobile device in a cool place whenever possible and keep it out of direct sunlight when flying outdoors.
Further solution:
We will continue to optimize the DJI Pilot app, increasing computation efficiency and lowering power consumption to ensure that it always runs smoothly
Flickering screen and/or a blank screen during flying.
Reason: When the Phantom is flying at an extended distance, the angle of the antennas is essential to maintain a strong signal.
Solution: Refer to the user manual and adjust the antenna angle. i.e. the type of settings on the device or the video card in the Phantom unit.
DJI Customer Service North America