Hello Bryan Andrews,
This is a known issue with design time when you try to change a property after running the project without closing the form in design time. Unfortunately, it is not only RadTreeView that is involved in this scenario, but the Visual Studio design time as well.
We are working on a solution but cannot give you a specific time frame. Please, check back with us next month and we will update you on our progress.
Thank you for your time.
the Telerik team