I suspect they aren't actually installing the app if you have "Allow use
of iTunes Store (supervised only)" deselected in your configuration
profile. They could just be creating a web clip to the Netflix web page
which looks like an app. If you want ...
Just keep trying with your entire selection. It will eventually work. I
can do 15000 iPads at once, but 4/5 times it will fail. I just keep
using the back in my browser, if you use the back button in the UI, it
goes out of the prestage completely.