BackStage closing

Hi, here is simple example to reproduce issue:

<ribbon:RibbonWindow x:Class="TestBackStage.Shell"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:docking="http://schemas.actiprosoftware.com/winfx/xaml/docking"
xmlns:ribbon="http://schemas.actiprosoftware.com/winfx/xaml/ribbon"
xmlns:themes="http://schemas.actiprosoftware.com/winfx/xaml/themes"
xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
mc:Ignorable="d"
WindowStartupLocation="CenterScreen"
RenderOptions.ClearTypeHint="Enabled"
ShowInTaskbar="True"
MinHeight="480"
MinWidth="640" 
d:DesignHeight="480"
d:DesignWidth="640"
AllowsTransparency="False"
themes:ThemeProperties.IsTransparencyModeEnabled="False">
<ribbon:RibbonWindow.Resources>
		<Style TargetType="{x:Type TextBlock}" x:Key="ReadOnlyValueStyle">
			<Setter Property="Margin" Value="12,0,0,0"/>
			<Setter Property="Foreground" Value="Gray"/>
			<Setter Property="Height" Value="22"/>
			<Setter Property="Width" Value="150"/>
			<Setter Property="VerticalAlignment" Value="Center"/>
			<Setter Property="FontSize" Value="12"/>
			<Setter Property="SnapsToDevicePixels" Value="True"/>
			<Setter Property="HorizontalAlignment" Value="Left"/>
		</Style>

		<Style TargetType="{x:Type TextBlock}" x:Key="NameStyle">
			<Setter Property="Foreground" Value="Black"/>
			<Setter Property="Height" Value="22"/>
			<Setter Property="FontSize" Value="12"/>
			<Setter Property="SnapsToDevicePixels" Value="True"/>
		</Style>
	</ribbon:RibbonWindow.Resources>
	<DockPanel>
		<!-- Ribbon Control -->
		<ribbon:Ribbon x:Name="_ribbon" DockPanel.Dock="Top" >
			<ribbon:Ribbon.ApplicationMenu>
				<!-- Backstage (Could alternatively use ApplicationMenu control) -->
				<ribbon:Backstage x:Name="appMenu">
					<ribbon:BackstageTab Name="Info" Header="Info" KeyTipAccessText="I">
						<DockPanel Margin="18,0,0,0">
							<ribbon:Separator DockPanel.Dock="Top" Label="Document Properties" Context="BackstageItem"/>

							<Grid Grid.Row="1" Margin="10,10,0,0">
								<Grid.ColumnDefinitions>
									<ColumnDefinition Width="Auto"/>
									<ColumnDefinition Width="*" />
								</Grid.ColumnDefinitions>
								<Grid.RowDefinitions>
									<RowDefinition Height="Auto"/>
									<RowDefinition Height="Auto"/>
									<RowDefinition Height="*"/>
								</Grid.RowDefinitions>

								<TextBlock Text="Name"
										   Grid.Row="0"
										   Grid.Column="0"
										   Style="{StaticResource NameStyle}"/>

								<TextBlock
										Text="NewDocument1"
										x:Name="name"
										Grid.Row="0"
										Grid.Column="1"
										Style="{StaticResource ReadOnlyValueStyle}"/>

						

								<TextBlock Text="Status"
										   Grid.Row="1"
										   Grid.Column="0"
										   Style="{StaticResource NameStyle}"/>

								<ribbon:PopupButton Label="Draft"
										FontSize="12"
										Grid.Row="1"
										Grid.Column="1"
										Context="BackstageItem"
										VariantSize="Small"
										Margin="9,-6,0,0"
										Padding="1,0,1,1"
										Foreground="Gray"
										HorizontalAlignment="Left"
										VerticalAlignment="Center"
										VerticalContentAlignment="Center"
										Height="21">
									<ribbon:Menu ItemVariantSize="Small">
										<ribbon:Button Label="Draft"/>
										<ribbon:Button Label="Final"/>
									</ribbon:Menu>
								</ribbon:PopupButton>
							</Grid>
						</DockPanel>

					</ribbon:BackstageTab>
				</ribbon:Backstage>
			</ribbon:Ribbon.ApplicationMenu>

			<ribbon:Ribbon.Tabs>
				<ribbon:Tab Label="Home" KeyTipAccessText="H">
					<ribbon:Group Label="Clipboard" />
					<ribbon:Group Label="Editing" />
				</ribbon:Tab>
			</ribbon:Ribbon.Tabs>
		</ribbon:Ribbon>

		<docking:DockSite
				x:Name="_site"
				x:FieldModifier="public"
				ToolWindowsHaveOptions="False" 
				ToolWindowsHaveTitleBars="True" 
				AreDocumentWindowsDestroyedOnClose="True" 
				CanToolWindowsRaft="False" 
				CanToolWindowsClose="True" 
				CanToolWindowsAutoHide="False"
				AutoHidePerContainer="False">
			<docking:SplitContainer Orientation="Vertical">
				<docking:SplitContainer Orientation="Horizontal">
					<docking:ToolWindowContainer x:Name="_left" docking:DockSite.ControlSize="130, 500" />
					<docking:Workspace>
						<docking:TabbedMdiHost IsImageOnTab="True">
							<docking:TabbedMdiContainer x:Name="_tabbedMdiContainer" />
						</docking:TabbedMdiHost>
					</docking:Workspace>
					<docking:ToolWindowContainer x:Name="_right" docking:DockSite.ControlSize="500, 500" />
				</docking:SplitContainer>
				<docking:ToolWindowContainer x:Name="_bottom" docking:DockSite.ControlSize="500, 100" />
			</docking:SplitContainer>
		</docking:DockSite>
	</DockPanel>
</ribbon:RibbonWindow>

 When i click on any PopupButtom item backstage closing. I expect that menu close on menu item click and backstage don`t.