I have the same issue. I used the GUI to program my Harmony One remote using the FireTV controller option. All of the keys mapped except for the back button. Interestingly, when I push the back button on the Harmony One remote when programming, Windows 8 also toggles to the main touch screen menu. When I toggle back to the Desktop, Flirc does say it recorded the key. Any ideas how to get this one key to work?