ArgumentException when changing DataContext

I get the following error:

It occurs, every time I change the DataContext of my Control. I have 3 GroupModel3Ds bound to different ObservableElement3DCollections like so:

<hx:GroupModel3D ItemsSource="{Binding SxxBoxes}" IsRendering="..." />
<hx:GroupModel3D ItemsSource="{Binding SyyBoxes}" IsRendering="..." />
<hx:GroupModel3D ItemsSource="{Binding SzzBoxes}" IsRendering="..." />

This only occurs, when I update the DataContext which already has Items in ItemsSource!

[leonbohmann]

Maybe that error occurs because I have a GroupModel in a GroupModel in a DataTemplate of an ItemsModel?

[holance]

Could you create a sample demo to show this issue?