File pickers do not work on Windows Phone

If you use Qt system file dialogs to access any resource on Windows Phone (8.1 or 10) the dialog will appear correctly but after picking any file, but it never seems to register back to Qt. I.e visibility changes to true but not back to to false, accepted() is never emitted and current file doesn't change despite the native dialog closing correctly.

This can be reproduced in the systemdialogs QtQuickControls (1) example (with the "Pictures library" capability added to the manifest).