Video bookmark/offmark

I’ve set up a kind of bookmark/note points for video. Ie, you click a point on the timeline and the video jumps to it.

Problem is some videos, some boomarks don’t sync with the point in the video, so when you press the point, the scrubber jumps varying amounts away from the bookmark.

 
controlbar.loader.jackel["in"+z]._x = (bookMarkPoint/duration)*298.3;
// bookmark/duration*length of timeline

what befuzzles me is how its so close or right on the line, yet with others it “all over the place” as it were.

any help? thanks