My application performs an automatic layout restoration during launch.
The call is done from the page constructor.

To produce the issue, we perform the following:

1. Drag a LayoutAnchorableFloatingWindow to a second monitor
2. Maximize it
3. Save layout
4. Restart application
   When this is done, the LayoutAnchorableFloatingWindow is not restored to maximized state.

After some testing it seems this is caused by a small piece of the restoration logic being run in the wrong thread.

Specifically, the Show call is being done via Dispatcher.BeginInvoke() while WindowState property is set outside of this.

I have made changes to correct the behavior by moving the setting of WindowState to within the same scope as Show(), and will create a pull request.