DJM - 900 Headphone output problems?

I recently noticed that a problem has come up on my DJM-900. While playing a track and my headphones plugged in if i cue an individual channel the cue will come out on one side of my headphones and then when I cue master it would come out on the other side of my headphones. seems like stereo panning of some type? not exactly sure why but this problem just recently started occurring.