LoadLevelAsync stuck in standalone occasionally

Hi All,

Like many others, I try to use LoadLevelAsync() to create a loading screen while loading the next level in our game. But then I run into this weird behavior. The loading works fine in the editor but not in the standalone build. In the standalone build, the progress would stuck at ~90% and never finish. But if you tab out the game and switch back to the game, the loading will be finished.

Here is my load coroutine:

 public IEnumerator LoadLevelHandler(int levelId)
 {
     yield return null;
     AsyncOperation async = Application.LoadLevelAsync(levelId);
     float showPortion = 0.0f;
     while (async.progress < 1.0f)
     {
         if (constantLoop)
         {
             SetLoadingImageFill(showPortion += Time.unscaledDeltaTime);
             if (showPortion > 1.0f)
                 showPortion = 0.0f;
             yield return null;
         }
         else
         {
             SetLoadingImageFill(async.progress);
             yield return null;
         }
     }
     yield return async;
 }

Any idea on what happened?