UWP app localization not working on release build

Question

I have my UWP app localized to English and German. However if I run the app the language changes properly. But when I give a release build the language doesn't change.

This is the code where I set the language to preferred language.

            var localSettings = Windows.Storage.ApplicationData.Current.LocalSettings;

            if (localSettings.Values.ContainsKey("LanguagePreference"))
            {
                 selectedLanguage = (string)localSettings.Values["LanguagePreference"];
                
            }
            Context = ResourceContext.GetForCurrentView();

            var lang = new List<string> { selectedLanguage };
            Context.Languages = lang;
            ResourceStringMap = ResourceManager.Current.MainResourceMap.GetSubtree(@"Util\Resources");

This is how I change the language from dropdown

private async void MenuFlyoutItem_Click(object sender, RoutedEventArgs e)
    {
        Frame.CacheSize = 0;
        Windows.Globalization.ApplicationLanguages.PrimaryLanguageOverride = "de-DE";
        ApplicationData.Current.LocalSettings.Values["LanguagePreference"] = "de-DE";

        await Task.Delay(100);
        Frame.Navigate(this.GetType());
    }

What am I missing here? any configurations? any files needed with the release?