On UWP, when tabbing around a ContentPage that isn't a NavigationPage, the focus moves as expected. However, if a NavigationPage is being used, the focus disappears for a minimum of one tab. If I run the accessibility sample found at https://docs.microsoft.com/en-us/samples/xamarin/xamarin-forms-samples/userinterface-accessibility/ on UWP, tabbing around the pages results in the focus disappearing for one tab stop on each page. That's the case whether or not the page has a back button.
Using that sample, on the main page, the focus goes from the "Automation Properties" button, to the "Tab Order" button, then disappears for one stop, then cycles back to the "Automation Properties" button again.
Does anybody know where the focus goes? And depending on where it goes, how to make it either visible/responsive or to stop it going wherever it is?
(In the app that I am working on, the focus disappear for 3 tab stops on each NavigationPage. I'm hoping identifying where it goes in the simpler case of the Xamarin accessibility sample will help identify what happens in more complex cases).