VisualTree problem

Hello Walter,
In this link:!258
You can download a test application that I created.
In this test application, I used with MVVM light toolkit, GraphLinkModel, TreeLayout and a node template with single port in left side & some ports in right (Button).
I use with EventTrigger behavior ti raise the Click event in viewmodel.
when I click on a right port, the next node was opening. I continue to click on the next node right port, and continue with this action again and again.
After a 7 or 8 generations, the ports stop raises the event trigger, and the next node doesn’t open anymore.
In output window in visual studio I can see Binding Error from this EventTrigger (I used with relativesource FindAncestor).
I debug the application and see that the last opening nodes doesn’t show in the “WPF VisualTree”.
Can you tell me why?
Thank you,

I haven’t had the chance to look at your app yet.

Parts that are “off-screen” might not be in the visual tree.
However, I’m not sure that would explain why you have that binding error.

Hi Walter,

Please take a look of the application and let me know if you have an opinion, I think the visualtree is not reflecting the nodes and from my modest point of view is a bug in the tool.
But maybe there is another reason related to the WPF behavior.