Audio freeze with cdj 2000nxs2

If i use rekorbox dj connected in hid to my cdj 2000 nexs2 connected with usb everything is perfect,
If i connect a usb stick and obviously try to switch to usb
Into the cd that is not playing all the rekordbox freeze for 5 seconds and stop the audio. This happens from i update the cd to the new firmware 1.40 with the old one i can switch to usb and use sticks without problem. I don't use hub just 2 cables in 2 usb ports. It's a problem because i'm djing with rekordbox dj and the other dj in the club use usb sticks and we can't switch without stopping the audio. Why all stop if i'm not using that cd to play? Can i downgrade to 1.31 the nxs2 ??? Let me know. I have all update to the new stuff osx, rekordbox and the cdjs. Help me