DJM 900 Nexus sound disappearing from one side

Hi! I've noticed a really irritating problem with my DJM-900 Nexus White. When I'm playing out the sound suddenly disappears from one side for a brief moment. I usually notice this when I'm using headphones and the sound has disappeared from the left monitor and first I thought that there might be a problem with my headphones, but now I've noticed that the sound also disappears from the PA as well. However after few seconds the sound comes back and this happens every now and then. Anybody know why this happens?

(I've also made sure that the problem isn't with my CDJ-2000's since the signal still comes normally for mixers L/R from both CDJ's)