Hello,

So in my DJI GO App in the WiFi settings section, I have two options: Auto and Custom. Since I linked my remote with the aircraft, it worked only with auto settings, using by default 5.8Ghz on channel 143 (or something). Because I couldn't find a switch between 2.4 and 5.8, I assumed that switching on Custom and then picking a channel between 1-11 will logically go to 2.4Ghz. So I've done that. A little popup appeared telling that everything will work after reset and then grayscale screen. The thing is that nothing reconnects again. I tried to search the network in my Galaxy S7 wifi list, and there is nothing. I reseted both the aircraft and the controller and the controller network appears in list like for 1 second and then dissapears. I observed that, if I turn off both aircraft and controller and then power on only the controller, the network is there and it connects with the smartphone, telling in app that is under 2.4 Ghz in Camera View mode. If I power on the aircraft too, the wifi connections drops and I'm back again. No more wifi network available. The only solution is to make the link again hadrcore using keys combination. After linking again, it goes to Auto settings and 5.8Ghz.

My question is: How should I properly switch from 5.8Ghz to 2.4Ghz using last DJI app version. Thank you !

Same thing happened to me today, but I fixed it by connecting my phone to the RC with an OTG cable. I would like to know an answer to that question as well...

This has happened because the remote control uses two wifi signals: one connects to the drone, and one to the phone. One is always 2.4, while the other is 5.8. If you set it to use 2.4Ghz, it'll try to connect to your phone using 5.8Ghz. Unfortunately, in the EU many phones cannot actually receive that band, so your wifi drops and your phone can no longer connect. As you have discovered, one solution is to use OTG  (DJi does not officially support OTG, blah, blah, blah...), or alternatively, you can reset your Spark and remote control so that they use 2.4 Ghz to connect to your phone again. To do this:

Switch on the Spark. Press the power button down for nine seconds. You will hear a total of six beeps: beep....beepbeep...beepbeepbeep. This will reset the Spark to its factory settings.
Switch on the remote. Press the power button down for nine seconds. Again, you will hear a total of six beeps.

Now switch them both off.
Switch on the remote control.
Switch on the Spark, and press the power button for three seconds until you hear one beep.
Press the function, custom (not the camera button!) and pause buttons all at once to re-pair the Spark and the remote. When the LED on the controller goes green, it has connected.

Your remote controller's wifi should now be reset to its default settings and you should be able to connect. I did exactly the same thing to my Spark when I was messing about with it once

Hope this works for you. It took me a few attempts to get it right.