Tween class - rollover flicker

1

I’m using the tween class from Kirupa’s tutorial. My buttons are animating correctly when I move the mouse slowly between them but if I move my mouse quickly back and forth between buttons they jump instead of animating smoothly. Rather than gradually animating between their start and end positions the buttons seem to jump to their start and end positions. Here is my code and I’ve attached my file. Thanks!

stop();
import mx.transitions.Tween;
import mx.transitions.easing.*;
//
checkerColor_mc;
// Street Up/Down
function streetDown(street_mc) {
	var tw:Tween = new Tween(street_mc, "_y", Strong.easeOut, 81, 90, 30, false);
}
function streetUp(street_mc) {
	var tw:Tween = new Tween(street_mc, "_y", Strong.easeOut, 90, 81, 30, false);
}
// Swim Up/Down
function swimDown(swim_mc) {
	var tw:Tween = new Tween(swim_mc, "_y", Strong.easeOut, 81, 90, 30, false);
}
function swimUp(swim_mc) {
	var tw:Tween = new Tween(swim_mc, "_y", Strong.easeOut, 90, 81, 30, false);
}
// Sport/Active Up/Down
function sportDown(sport_mc) {
	var tw:Tween = new Tween(sport_mc, "_y", Strong.easeOut, 81, 90, 30, false);
}
function sportUp(sport_mc) {
	var tw:Tween = new Tween(sport_mc, "_y", Strong.easeOut, 90, 81, 30, false);
}
//
// Button Rollover States
street_mc.onRollOver = function() {
	swimDown(swim_mc);
	sportDown(sport_mc);
};
street_mc.onRollOut = function() {
	swimUp(swim_mc);
	sportUp(sport_mc);
};
swim_mc.onRollOver = function() {
	streetDown(street_mc);
	sportDown(sport_mc);
};
swim_mc.onRollOut = function() {
	streetUp(street_mc);
	sportUp(sport_mc);
};
sport_mc.onRollOver = function() {
	swimDown(swim_mc);
	streetDown(street_mc);
};
sport_mc.onRollOut = function() {
	swimUp(swim_mc);
	streetUp(street_mc);
};