Judging by the provided exception, it looks like somehow you ended up with two controls on your form having the same auto-generated ID. Can you please open each fo the controls in the form, and check in its advanced properties for the value of the ID property - there should be some controls that have the same value C003 - you can change it to any unique alphanumeric value, and this should fix the problems. If any issues persist, please do not hesitate to let us know, we'll be glad to help you further.
the Telerik team
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