How to fix the STICK EMI 1 DJI controller error
To fix the STICK EMI 1 DJI controller error you need to use a small magnet to de-gauss the antennas. There are plenty of YouTube videos to show you how to do this but you have to watch the video to see how.
Putting the controller through the cat flap seems to work. The magnet on the flap seems to degauss the controller antennas.
Any small magnet probably would have done the job but I was wondering where I could find one.
A textual explaination
A YouTube video or a lengthy post on the DJI Forum reveals an answer but in many cases, I find, all you really want is to be told how to do something.