I am facing an issue often on my Nokia Lumia 720. On holding the back button, all the apps running disappear and the screen blackens. Then after a few seconds multiple start screen appear. This happens often when 4-5 apps are open in background. And when I tap the start screen thumbnail in the app switcher, a never ending loading screen appears. Is anyone else facing this issue? Does anyone have solution other than having a hard reset because that didn't work for me?