CDJ2000Nexus "E-8302 Cannot Play Track(000D)"

Hey guys, I have a big problem with my two CDJ 2000 Nexus. During my set i'm choosing a song it will load it, and few seconds later it tells me "E-8302 Cannot Play Track(000D)" after i'm trying to find another song and it says "Now Loading" it just freeze. So the only thing i can do is close the CDJ and restart it. Any ideas why it continues to freeze?  It doesn't do it every time it just randomly does it. The firmware is Updated to version 1.21. And it does it with randomly song and USB. 

My setup is :

DJM-900 Nexus, 2(CDJ's 2000 Nexus)