Sharepoint 2013 third level navigation

I have a custom master page and want to change the Navigation to have up to three levels as separate unnumbered lists.

So I modified the master page und using the following code:

<SharePoint:DelegateControl runat="server" ControlId="TopNavigationDataSource" Id="topNavigationDelegate">
    <Template_Controls>
        <asp:SiteMapDataSource
            ShowStartingNode="False"
            SiteMapProvider="SPNavigationProvider"
            id="topSiteMap"
            runat="server"
            StartingNodeUrl="sid:1002"/>
    </Template_Controls>
</SharePoint:DelegateControl>
<asp:ContentPlaceHolder id="PlaceHolderTopNavBar" runat="server">
    <SharePoint:AspMenu
        runat="server" 
        UseSeparateCss="false"
        AdjustForShowStartingNode="False" 
        StaticDisplayLevels="2"
        AccessKey="1"
        SkipLinkText="" 
        EnableViewState="False"
        MaximumDynamicDisplayLevels="0" 
        DataSourceID="topSiteMap" 
        Orientation="Horizontal"
        RenderingMode="List"
        UseSimpleRendering="False"
        ID="TopNavigationMenu">
        </SharePoint:AspMenu>
</asp:ContentPlaceHolder>

<asp:ContentPlaceHolder id="PlaceHolderTopNavBar2" runat="server">
    <SharePoint:AspMenu
        runat="server" 
        UseSeparateCss="true"
        AdjustForShowStartingNode="false" 
        StaticDisplayLevels="1"
        AccessKey="1" 
        SkipLinkText="" 
        EnableViewState="True"
        MaximumDynamicDisplayLevels="0" 
        DataSourceID="topSiteMap2" 
        Orientation="Horizontal"
        RenderingMode="List"
        UseSimpleRendering="false" 
        ID="TopNavigationMenu2">
        </SharePoint:AspMenu>
</asp:ContentPlaceHolder>

<asp:ContentPlaceHolder id="PlaceHolderTopNavBar3" runat="server">
    <SharePoint:AspMenu
        runat="server" 
        UseSeparateCss="true"
        AdjustForShowStartingNode="false" 
        StaticDisplayLevels="1"
        AccessKey="1" 
        SkipLinkText="" 
        EnableViewState="True"
        MaximumDynamicDisplayLevels="0" 
        DataSourceID="topSiteMap3" 
        Orientation="Horizontal"
        RenderingMode="List"
        UseSimpleRendering="false" 
        ID="TopNavigationMenu3">
        </SharePoint:AspMenu>
</asp:ContentPlaceHolder>

This is working as long there are really 3 levels of pages. The problem occurs when there is no third level. In such case the 2 level is rendered twice. I have no clue why?

Can anybody give me an advice what to change please! :-)

Regards,

Christian