DJM-900nexus digital audio channel problems

I have my CDJ 2000's plugged into my DJM 900nexus through the digital audio coax cables. when i plug it into channel 3 (on the mixer) it plays through channel 1 as well. However, when plugged into channel 1, it doesn't play in channel 3. seems like a hardware problem, crossed wires maybe? 

Can anyone provide some feedback if they have had the same issues?

Cheers, DJ TRV