Using LoadFromCacheOrDownload causes iOS to freeze/stall

We have the below code. On Android, the code reports a smooth progress from 0 to 1. On iOS, it jumps straight from 0 to 1. This is also exhibited in the foreground as when we load the asset bundle for the first time the whole app freezes until the bundle successfully loads. A couple of things to consider: - The problem is iOS specific. it works on every other platform. -we do not ship for webplayer - It successfully loads the assets on iOS - so definitely built for the platform - We download assets over the internet in this particular situation, so we are not loading from streaming assets - When we download, we save to a location on disk. Only after the content is 100% downloaded do we then load the bundle. - Said another way: WWW.LoadFromCacheOrDownload is given a local path to load the bundle from - Line 10 is yield every frame NOT every cpu cycle. So it is not maxing out the CPU. - To reiterate: The below code loads the bundle correctly - it just does not report on progress in a granular way AND the app freezes while loading the bundle What we would prefer to see is a loading process that is smoother - allowing us to at least show a graduated progress bar or whirly gig. Why is this? Is there anything we can to do mitigate?

var threadPriority = priority == AssetPriority.Foreground ? ThreadPriority.High : ThreadPriority.Low;
Application.backgroundLoadingPriority = threadPriority;
using (var www = WWW.LoadFromCacheOrDownload(url, 1)) {
    Trace.Log(string.Format("{0} {1} Priority: {2}", LocalPackagePath, ContainerPath, priority));
    www.threadPriority = threadPriority;
    Application.backgroundLoadingPriority = www.threadPriority;
    Trace.LogDiag(string.Format("{0} STARTING LoadFromCacheOrDownload", LocalPackagePath));
    Script.StartCoroutine(RunWWW(www));
    do
    {
        yield return 0;
        Trace.LogDiag("Progress: " + www.progress);
    } while (!www.isDone && String.IsNullOrEmpty(www.error));
    Trace.LogDiag(string.Format("{0} END LoadFromCacheOrDownload", LocalPackagePath));
    if (!String.IsNullOrEmpty(www.error) || www.assetBundle == null) {
        // we received an error loading the bundle
        // as the bundle is local, chances are the bundle is corrupted by something.
        // We delete and move on...
        Trace.LogError(string.Format("{0} Error loading bundle @ {1}: {2}", LocalPackagePath, ContainerPath, (String.IsNullOrEmpty(www.error) ? "Unknown" : www.error)));
        yield break;
    }
    Bundle = www.assetBundle;
    Bundle.name = ContainerPath;
}

... and:

private IEnumerator RunWWW(WWW www)
{
    yield return www;
}