I beleive what you are saying is right but I couldn't simulate the issue with this demo: http://demos.telerik.com/silverlight/#TreeView/FirstLook
Can you please describe the steps in more detail: how much time one should keep clicking on the expander (2-3-4 minutes); should the opposite operation wait for the animation to complete.
Finally it would be great if you provide us a simple screen cast demonstrating the issue.
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