Sorry for the long delay.
To reproduce this we went to: Control Panel -> Appearance and Personalization -> Display and set to "Medium - 125%" which will prompt a restart.
After restarting we went into our application and opened the Backstage. We then resized the application window so that it was smaller than our Backstage (Buttons and BackstageTabs). We were unable to access the items on the bottom of the backstage menu because the window was too small and there was no way to scroll the overall backstage contents.
Hope this helps,
Joe