My Controller gl 300 f Can Not be Update becaus Assistant sag’s device Not supportet ….I have  Right Assistant installed. Three or Four times …
In the DJI Go App the Controller have no Firmware …
So i have Problems With Video transmission  …..some one an idea.

Hello, there. Sorry for the inconvenience. May we know which DJI Assistant 2 you are using? And its version is?

DJI Assistant2 For Phantom Version 2.0.10(4)
I wonder that in DJI go4 i Can only read Controller Firmware unknown
I Can controll Phantom but only Weak transmission Signal

Der Linzer Posted at 12-14 08:53
DJI Assistant2 For Phantom Version 2.0.10(4)
I wonder that in DJI go4 i Can only read Controller Firmware unknown
I Can controll Phantom but only Weak transmission Signal

Hi, there. Sorry for the late response. Kindly know we can receive notification only if you reply to our post directly. We confirmed that only the standard remote controller (GL300L) of Phantom 4 Pro 2.0 supports firmware updates via DJI Assistant 2, the other remote controllers don't support it.
For GL300F, you may try to upgrade it with DJI GO 4:
Turn on the remote controller and connect it with DJI GO 4. Upgrade the firmware following the instructions on the app. Make sure that your mobile device is connected to a mobile or Wi-Fi network.
In case you need it. here is the link to install the latest version of DJI GO 4: https://www.dji.com/downloads/products/phantom-4-pro

Same problem as mine, the latest firmware for the drone and the controller totally ruins the video transmission making it impossible to fly. The only fix is to downgrade the firmware, but DJI have removed all means to do it. I found a program online that allows you to downgrade firmware and it fixed my drone. The latest firmware is your problem.