Moreover, if you are using AJAX on the page - disable it and see if there is a server-side error thrown. You can easily turn off AJAX by setting the EnableAjax
property of RadAjaxManager
In case the issue persists please send us the markup of the page with the related code-behind so we can examine it.
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Telerik UI for ASP.NET AJAX is ready for Visual Studio 2017 RC! Learn more.