CDJ 350 problems with rekordbox

I have managed to setup my two CDJ 350 and DJM 350 mixer  with rekordbox. Everything works expect when im busy playing a song on deck 1  and want to load a song onto deck 2 with the push select button or even just using my laptop to drag a song onto deck 2 , the sound on deck one stops and on the mixer the level indicator light on the channel goes away. I then have to push play on the deck 1 so that it starts playing again. What could be the problem? I can also mention on my laptop in rekordbox the songs are still playing.