pre-listening CUE button won't prevent music to be heard on output

I am using only my MACbook, Traktor 2 big speakers and my headphone.

I am playing deck A on the output and that is ok.

Now, I want to pre-listen to deck B by myself before letting everyone listen to both decks on the output.

But it doesn't work! Both Tracks an be heard from the output even though I click CUE button to Pre-listen one of them.

The CUE button is the one(found at the center, just below the mixer section of the hardware, there are 4 CUE buttons in my case since I have the Traktor S4.

Actually if I click on the CUE button (found at the center, just below the mixer section of the hardware) I hear the music louder inside the headset, and when the CUE button is disabled I can still listen to the music on the headset but at lower volume.

But the point is not that, the point is that I cannot pre-listen the track without anyone listening to it.

Settings are fine and level of the audio on headphones is good and also the mixer knob

thank you in advance