The default design for all our ScrollViewers changed with the last CTP. I am sorry to hear that the change has been an issue for you. I will communicate what you have written to our design team.
It is unfortunate that you are not moving forward with the new versions because of the changed design. Therefore I am attaching a xaml file with a Template for the RadTreeView where the ScrollViewer has its default theme. To use this template, put it in your resources (in the App resources it will be discoverable by all controls) and set it as a template for all the tree views, like so:
Again, I am sorry for the inconvenience. Thank you for your feedback on moving on with the new versions, come back to us if you have more issues or questions.
All the best,
the Telerik team
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