Created Unassigned: Switching from AutoHide to Float [17739]

When am switching layoutanchroablepane from autohide to float, black background appearing in the area of the layoutacnchroblepane for a sec.

<Window x:Class="TestProject.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:ad="http://schemas.xceed.com/wpf/xaml/avalondock"
Title="MainWindow" Height="500" Width="700">
<Grid>
<ad:DockingManager>
<ad:LayoutRoot>
<ad:LayoutPanel>
<ad:LayoutAnchorablePaneGroup>
<ad:LayoutAnchorablePane>
<ad:LayoutAnchorable Title="Panel1"/>
</ad:LayoutAnchorablePane>
</ad:LayoutAnchorablePaneGroup>
<ad:LayoutAnchorablePaneGroup>
<ad:LayoutAnchorablePane>
<ad:LayoutAnchorable Title="Panel2"/>
</ad:LayoutAnchorablePane>
</ad:LayoutAnchorablePaneGroup>
</ad:LayoutPanel>
</ad:LayoutRoot>
</ad:DockingManager>
</Grid>
</Window>