Changing visibility of tab within ContextualTabGroup while backstage is open

When changing the visibility of a tab within a ContextualTabGroup to Collapsed while application is in backstage and then manually closing the backstage causes a rendering problem of the tab-group.
When changing the visibility within a command that automatically closes the backstage, the problem doesn’t occur.

Used the following code (Within a new project):

App.xaml.cs:

protected override void OnStartup(StartupEventArgs e)
{
    base.OnStartup(e);
    ThemesOfficeThemeCatalogRegistrar.Register();
    ThemesMetroThemeCatalogRegistrar.Register();
    RibbonThemeCatalogRegistrar.Register();
    ThemeManager.CurrentTheme = ThemeName.MetroWhite.ToString();
        }

 MainWindow.xaml:

<ribbon:RibbonWindow x:Class="WpfApplication1.MainWindow"
                     xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
                     xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
                     xmlns:ribbon="http://schemas.actiprosoftware.com/winfx/xaml/ribbon"
                     IsGlassEnabled="False"><ribbon:Ribbon Name="Ribbon"><ribbon:Ribbon.ApplicationMenu><ribbon:Backstage><ribbon:BackstageTab Header="Test"><Grid><Grid.RowDefinitions><RowDefinition Height="*"></RowDefinition><RowDefinition Height="*"></RowDefinition></Grid.RowDefinitions><ribbon:Button Grid.Row="0" Label="Hide second tab and close backstage manually"
                                       StaysOpenOnClick="True" Click="CollapseSecondTab" /><ribbon:Button Grid.Row="1" Label="Hide second tab and close backstage automatically"
                                       StaysOpenOnClick="False" Click="CollapseSecondTab" /></Grid></ribbon:BackstageTab></ribbon:Backstage></ribbon:Ribbon.ApplicationMenu><ribbon:Ribbon.ContextualTabGroups><ribbon:ContextualTabGroup Label="Group" IsActive="True"><ribbon:Tab Label="Tab1"></ribbon:Tab><ribbon:Tab Label="Tab2" Name="Tab2"></ribbon:Tab></ribbon:ContextualTabGroup></ribbon:Ribbon.ContextualTabGroups><ribbon:Ribbon.Content><ribbon:Button Label="Show second tab" Click="ShowSecondTab"></ribbon:Button></ribbon:Ribbon.Content></ribbon:Ribbon></ribbon:RibbonWindow>

 MainWindow.xaml.cs:

private void ShowSecondTab(object sender, ExecuteRoutedEventArgs e)
{
    Tab2.Visibility = Visibility.Visible;
}
private void CollapseSecondTab(object sender, ExecuteRoutedEventArgs e)
{
    Tab2.Visibility = Visibility.Collapsed;
}

To reproduce the problem make sure both tabs within the tab group are shown. -> Open the backstage -> Click "Hide second tab and close backstage manually"-button. -> Close the backstage.

Any suggestions, why this is happening and how to avoid/solve this problem?