Could you try removing the ClientIDMode=static property and test again? RadControls do not support this mode because most of them are complex containers and MS also recommend using the automatic mode for such containers.
I tried resolving the url like this and it seems to work as expected with me. I am attaching here the test files as a reference. In case removing the Static setting does not resolve the issue with you, can you reproduce the problem with my files and post the needed changes, so I can investigate the case?
All the best,
the Telerik team
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