There used to be this issue 2 years ago, but now, when I reinstalled recalbox to the latest version, I can't pair again.
In basic mode (on) and pair mode it finds all of my three controller, but when I want to pair then, it fails.
I tried it a dozen times with different firmware versions on my pads (4.10, 4.00, 2.00) without a change. I tried to reset the bt pairing, as well as a factory reset...nothing.