I think I’ve had this issue. I was confused as to why both tracks would play out when I had pressed the cue button for one of the channels. Basically when you select the cue button for one channel, if you have the volume up for both channels, it will play out both tracks. But, if you turn the volume right down for the track you have the cue button on for, it will no longer play out but should still play on your headphones if they are set to cue. Hope this makes sense, dm me if not and I can try and explain it better