DJJ 400 - Lights not working when in use (only Beat Sync flashes red)

Hi, when I'm using the DJJ 400 none of the lights work, except for the Beat Sync buttons which flash red.

I have tried resetting my computer and re-downlading Rekordbox and when I leave the controller to settle after powering up, all lights do work on the Standby mode (so I'm thinking it's not a hardware problem). Then, as soon as I begin using the controller all lights suddenly turn off (again, except for the Beat Sync's).

I'm hoping there's an easy solution to this, maybe I'm completely missing a simple trick? 

Thanks in advance.