Tween or enter frame bugs?

1

hello im new in flash !
I have created a code that basic move in randmom positions 3 opjects (mc , mc2 ,mc3) in 65 frame rate .

import fl.transitions.Tween;
import fl.transitions.easing.*;
import fl.transitions.TweenEvent;
import flash.events.Event;


var xs:Number = 550; // stage width
var ys:Number = 400; // stage height
var xyspace:Number = 30 * 2;
var xsa:Number = xs-(xyspace*2);
var ysa:Number = ys-(xyspace*2);
var speed:Number = 1 ;
var speedTimer:Number = speed * 1000;
var way = None.easeInOut ; 
var tof:Boolean = false; 

///////
var tff:Boolean = true;
addEventListener(Event.ENTER_FRAME , ch);
var myTweenx1 = new Tween(mc, "x", way, mc.x ,xyspace + Math.round(Math.random() * xsa), speed + 50 , tof);
var myTweeny1 = new Tween(mc, "y", way, mc.y ,xyspace + Math.round(Math.random() * ysa), speed + 50, tof);
function ch(e:Event){
   if (tff == true){
      var myTweenx1 = new Tween(mc, "x", way, mc.x ,xyspace + Math.round(Math.random() * xsa), speed + 50, tof);
      var myTweeny1 = new Tween(mc, "y", way, mc.y ,xyspace + Math.round(Math.random() * ysa), speed + 50, tof);
      tff = false;
      myTweenx1.addEventListener(TweenEvent.MOTION_FINISH, onFinish);
   }
}

function onFinish(e:TweenEvent):void {
tff = true;
}




/////////////////
var tff2:Boolean = true;

addEventListener(Event.ENTER_FRAME , ch2);
var myTweenx12 = new Tween(mc2, "x", way, mc2.x ,xyspace + Math.round(Math.random() * xsa), speed + 100, tof);
var myTweeny12 = new Tween(mc2, "y", way, mc2.y ,xyspace + Math.round(Math.random() * ysa), speed + 100, tof);
function ch2(e:Event){
   if (tff2 == true){
      var myTweenx12 = new Tween(mc2, "x", way, mc2.x ,xyspace + Math.round(Math.random() * xsa), speed + 100, tof);
      var myTweeny12 = new Tween(mc2, "y", way, mc2.y ,xyspace + Math.round(Math.random() * ysa), speed + 100, tof);
      tff2 = false;
      myTweenx12.addEventListener(TweenEvent.MOTION_FINISH, onFinish2);
   }
}

function onFinish2(e:TweenEvent):void {
tff2 = true;
}

//////////////
var tff3:Boolean = true;

addEventListener(Event.ENTER_FRAME , ch3);
var myTweenx13 = new Tween(mc3, "x", way, mc3.x ,xyspace + Math.round(Math.random() * xsa), speed + 150, tof);
var myTweeny13 = new Tween(mc3, "y", way, mc3.y ,xyspace + Math.round(Math.random() * ysa), speed + 150, tof);
function ch3(e:Event){
   if (tff3 == true){
      var myTweenx13 = new Tween(mc3, "x", way, mc3.x ,xyspace + Math.round(Math.random() * xsa), speed + 150, tof);
      var myTweeny13 = new Tween(mc3, "y", way, mc3.y ,xyspace + Math.round(Math.random() * ysa), speed + 150, tof);
      tff3 = false;
      myTweenx13.addEventListener(TweenEvent.MOTION_FINISH, onFinish3);
   }
}

function onFinish3(e:TweenEvent):void {
tff3 = true;
}

It works pretty good and do what i want but in random time the objects stop moving or only one object or only 2 . i cant understand why . The enterframe event stop of simple the tween never finish ?

tnx for your time !