Reply to S2 Sync Jitters?

Hey folks - As I continue to practice mixing and picking up cue points I notice that when i'm syncing one of the deck to the master deck sometimes the new song i'm cueing seems to be jumpy and jittery. I started noticing the past couple of days.

Please don't bash me for using auto sync. I'm a noob and would like to spend my time practicing transition rather than manual beat match.

is it traktor or is it my mp3s? Anyone else has had this issue? Please advise. Thank you.

Setup
Kontrol S2
Traktor Pro 2 with DJTechTools mapping
Macbook Pro 2Ghz i7 with 4GB RAM