We have tested the issue with the latest version RadAsyncUpload worked as expected. You can test it as well on our on-line demo here. If it still does not work please let us know the exact version of browser use on the device used so we could test it again and be more helpful.
the Telerik team
If you want to get updates on new releases, tips and tricks and sneak peeks at our product labs directly from the developers working on the RadControls for ASP.NET AJAX, subscribe to their blog feed