Often, after I load a new song into a deck and press Play on it, I hear it in my headphones.
The crossfader is all the way towards the currently playing song, and the Cue/Mix knob is all the way to Mix, but it sounds like a 50/50 blend of the two songs. Turning the Cue/Mix knob a bit and then back to Mix fixes the issue, but this should not be happening.
It may be a MIDI issue, or it may be a soundcard issue. I’m using a Traktor Audio 2, which doesn’t work with Djay very well. I have to pre-cue using the main audio out (plugging my headphones into my headphone jack) and have the main output come from the Traktor Audio 2.