Ok, Jason, now we're geting somewhere, since I can replicate the problem (a different problem) everytime.
First time I launch the app, the platform selection works. I press the right ou down arrow in any of the controllers (the small one or the game controller), and it works.
If I exit the app in the menu, it will never work again, unless 1) restart the shield; 2) force-close the app in the shield applications settings.
I tried to exit the app and get back in 20 times and it never worked, while previously (in the .21 version), it randomly would work (after 8, 10, 12 times, maybe).
Now it will always work the 1st time the app is run, and will never work again if you exit the app in the menu, until you force-close it.
Maybe now you'll be able to replicate it in your system too, hopefully.
Either way, now I know how to solve it on my own, so, even if you can't debug it, I will know what to do to solve it.
Many thanks for this new version (.22). Cheers!