My actionscript is not working properly

programming flash
1

I have some actionscript that starts off great, but then when the second image starts to come in the image starts to slow down till it stops, then after a second or two the image starts up again the way it should. Then after the images exit the screen after several seconds the images start going in reverse. Why in the world would my actionscript cause that to happen? I am using the class TweenLite.

import gs.TweenLite;
import gs.easing.*;

var clouds = 0;
var clouds2 = 2000;

this.logo_mc._alpha = 0;

function moveClouds():Void {
TweenLite.to(this.clouds_mc, 10, {_x: clouds - 2000, onComplete: moveClouds, onCompleteScope: this});
TweenLite.to(this.clouds2_mc, 100, {_x: clouds2 - 2000});

(clouds < -2000) ? (clouds = 2000) : (clouds - 2000);
(clouds2 == -2000) ? (clouds2 = 2000) : (clouds2 - 2000);
updateAfterEvent();

}

moveClouds();

TweenLite.to(this.logo_mc, 5, {_alpha: 100, ease: Normal.easeIn});