Agree totally. I also have a ROKU 3 and that has just been updated and works great. I have 4 AppleTV's (4K and 1080P versions) and on all they just sit there with a spinning buffer disc. This is definately an issue with the app.
Please Please get it sorted.
Their credibility is now at threat especially as they are supposed to be a broadcaster and a tech company. As far as I am concerened at the the moment they are neither!