Rekordbox DJ and CDJ-850 problem

Hello everybody.
I had a problem with a live transition from USB to the PC and vice versa.
My colleague is playing with USB Flash. When I want to replace it and want to play with Rekordbox DJ, I connect my MAC to the USB output CDJ-850 (which are on the rear of the player).
I tune the output channels on Recordbox DJ, then surfing is one of the players on the mode of PC. Now I have one player plays with USB, with a second Rekordbox DJ. When I switch the second player, it is in the mode of PC, playback stops Rekordbox DJ. This is very bad for the dance floor.
Similarly, on the contrary, if I play with Recordbox DJ on both players, and one of them switched to USB, playback is stopped on both players.
Is it possible to solve this problem?
I experienced a similar XDJ-1000, this problem does not arise, I could seamlessly move from playing both players with Rekordbox DJ to play with two players with USB (without link cable).