May 25, 2018 02:11 AM|Brando ZWZ|LINK
According to the error message, there are too many reasons why show this error.
For example, there are two content controls that had the same ID.
Could you please post the whole page's codes?
Does this page has the master page?
If you could post more details information and codes, it will be more easily for us to reproduce the issue and solution.