A simple scrollbar with easing, but a small glitch

I believe it was here that I once found this custom scroller. The problem is this: when you first use the dragger it spontaneously shifts a couple pixels to the left. I tried putting it into this position physically before publishing thinking it wouldn’t show if it already starts in the correct place. But it still shifts. That lead me to assume it was in the AS and that the starting position defined in the AS caused this. But for whatever reason I am still overlooking it. Anyone wanna find a quick solution?

http://www.justforthealofit.com/sample/jjScroller.fla

Furthermore, according to the movieclip properties, the dragger is at 404.4 for x position. But I put a trace(dragger._x) at the very top of the code and it reports that the initial x position is 409.85. If I change the x position and test, the reported number is always greater than what it really is. And no matter what, the left shift still occurs when the dragger is first clicked.