Reply to Cue button 'lag'

Hi, I'm getting weird lag with the cue buttons on the traktor s4, e.g. if I press a cue button sometimes it takes 1 second to actually play and sometimes I press the button and the cue point doesn't play! it also happens on my X1 but not so frequently, my cpu is at very low so it's not that. It's very laggy.
Also, if a deck isn't playing, and for example I hold cue button 1 and then press 2 and let go of 1, the track stops playing?! Why is this? I can't jump between cue points now.