I changed ticket type to "support" to be able to send you the latest internal build, which includes the fix.
Indeed the treeview does not honour focusable elements inside of widget's template. I confirm this as a bug, which we already addressed. As I mentioned, the latest internal build is attached to this message. Give it a try and let me know if the problem still persists.
As a gratitude for your involvement I have updated your Telerik points.
the Telerik team
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