Thank you for your question, P.
I will be glad to help you, however I have some clarification questions:
- How do you create your custom RadTreeView, have you used subclassing or some other approach?
- How do you assign the default theme to the TreeView?
It will be best if you can send us a sample project that we can use to investigate the issue locally. You can do so in a new support ticket.
the Telerik team