I have already answered your question in the opened support ticker, however, I am pasting my replay here for the rest of the community:
Thank you for contacting the Telerik Support Team.
Can you confirm that you use the smart tag and first click on the "Edit Templates" link at the bottom before modifying the controls inside and that once you are done you click the "End templates editing" option in the smart tag? This is the correct way to edit its ContentTemplate, so does following this procedure resolve the problem?
You can also find a short video that illustrates that in the attached archive.
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