If using MVVM bindings (AnchorablesSource and DocumentsSource) both the serialization and the deserialization of the layout is completely broken. Docking panels to the top or bottom won't get saved at all.
The easiest way to reproduce this is to check out this example: https://www.codeproject.com/Articles/719143/AvalonDock-Tutorial-Part-Load-Save-Layout where the saving still works and then update the AvalonDock to the latest version and see that the serialization is broken.
The easiest way to reproduce this is to check out this example: https://www.codeproject.com/Articles/719143/AvalonDock-Tutorial-Part-Load-Save-Layout where the saving still works and then update the AvalonDock to the latest version and see that the serialization is broken.