The problem is caused by the generated ID of the datepicker. You can try to modify datepicker in Date.ascx like so:
<%= Html.Telerik().DatePicker()
.Name(ViewData.TemplateInfo.HtmlFieldPrefix)
.HtmlAttributes(new{ id = ViewData.TemplateInfo.GetFullHtmlFieldId("") + DateTime.Now.Millisecond.ToString()})
.Value(Model > DateTime.MinValue? Model : DateTime.Today)
%>
Best wishes,
Georgi Krustev
the Telerik team
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