LayoutAnchorable.IsActive property is not working

[silviubogan]

Steps to reproduce:

1. Clone https://github.com/silviubogan/cs-extended-wpf-test-1
2. Start the program
3. Make the Data Grid the active tab by clicking on it
4. Click on the button at the top of the window
5. The Flow View tab should be active but the Data Grid is instead

I tested this with 3.5.0 (the version part of the Extended WPF Toolkit) and the same happens.

I've read this page but I did not find something useful.

The relevant part of the program, after the part which deserializes some XML with a changed layout:

var la = MyDockingManager.FindName("MyFlowViewAnchorable") as Xceed.Wpf.AvalonDock.Layout.LayoutAnchorable;

Dispatcher.BeginInvoke(new Action(() =>
{
    la.IsActive = true;
}));

No exception is thrown, no error is shown.

Thank you.