I've tested both joypads under Win10 at my PC and they worked fine. Accoridng to my observations, the pads disconnect when they're plugged in together. It doesn't happen when only one of them is plugged. Also, it seems that when I replug the dongles with Recalbox switched on, it sometimes helps to get rig of the disconnecitons. At least this is what I believe for the time being, I'm still testing it.
@JPMadman79 always use the parent when you can.
The only case where it's better to use a clone if when the parent doesn't work or for some 4-player multiplayer games where sometimes parent or clones are dedicated to a different number of players