Progressbar freezes. Bug of what?

Hi there,

Using this code to create progress bar.

  var PBWin = new Window ("palette", "Progress", [0,0,300,70]);
  var ProgressText = PBWin.add("statictext", [12,10, 190, 30], "Progress");
  var ProgressBar = PBWin.add("progressbar", [10,40,290,60], 0, 50);
  this.windowRef = PBWin;
  PBWin.show();
  PBWin.center();
  
  for(i=0; i<50; i++){
      
      ProgressBar.value = i;
      ProgressText.text ="Processing things "+(ProgressBar.value+1)+" from "+ 50; 
      PBWin.update(); 
      $.sleep (200);      
      }
  
  alert("Done");

But when I switch between the windows (fox example from AE to Chrome), progressbar freezes and I can define is it crashed or continuing to work in the background.

I`d be glad if someone could test and tell does it freeze for anyone else.