I have a feeling this is potentially related to the issue we encountered when the first opening of the Localization demo displayed a blank UI, which was subsequently displaying correctly during subequent re-openings of the Page:

Repro Steps:

1) Open the MiniShowcases InternalProject, and open Localization.xaml
2) 'Play' the Page, and use the Language dropdown to switch to Arabic.
3) 'Stop' playback of the Page, and close the Localizatioin.xaml Page by closing its Tab.

4) Re-Open Localization.xaml
Observe how Arabic is still present on-screen.

5) Close the Localizatioin.xaml Page by closing its Tab.

6) Re-Open Localization.xaml
Observe how English is now present on-screen.

Expected Results: The Data displayed on a Page is consistent between various openings of the file, provided nothing else has changed in the XAML or the Data.