InvalidOperationException occur when activate ToolWindow

Hello,

In our application, the following exception occur sometime when activate ToolWindow.

Would you please check it?

For now, I'm not sure if there is particular steps or condition.

And I cannot reproduce it in sample project. (Our application is the same structure of sample project of #26421)

System.InvalidOperationException: Specified element is already the logical child of another element. Disconnect it first.
at System.Windows.FrameworkElement.ChangeLogicalParent(DependencyObject newParent)
at System.Windows.FrameworkElement.AddLogicalChild(Object child)
at System.Windows.Controls.Decorator.set_Child(UIElement value)
at System.Windows.Documents.AdornerDecorator.set_Child(UIElement value)
at ActiproSoftware.Internal.mS..ctor(FrameworkElement , FrameworkElement , Boolean , Boolean , Boolean , Boolean , Boolean )
at ActiproSoftware.Windows.Controls.Docking.DockHost.otf(ToolWindow , Side )
at ActiproSoftware.Windows.Controls.Docking.DockHost.Dt5(ToolWindow )
at ActiproSoftware.Internal.kg.JnX(DockingWindow , Boolean )
at ActiproSoftware.Internal.kg.Activate(DockingWindow window, Boolean focus)
at ActiproSoftware.Windows.Controls.Docking.DockingWindow.Activate(Boolean focus)
at ActiproSoftware.Windows.Controls.Docking.DockingWindow.Activate()