Thank you very much for the project.
The problem is that we do not support scenarion where there's visual inheritance of TabStrip or Docking manager. Generally speaking, the visual inheritance might cause problems with any control.
For more information how to workaround this issue (changing access modifier
s) please read carefully following KB
I am attaching the fixed project that follows the instructions from the KB.
I hope this helps. Don't hesitate to contact us if you have other questions.
the Telerik team
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