Put more than two RadDatePicker with single SharedCalendar on page. some RadDatePicker are in side of UpdatePanel with a button in it. when I press that button RadDatePicker behaviour is strange. 
RadDatePicker inside UpdatePanel not opening Calendar popup while RadDatePicker outside UpdatePanel opens calendar popup but gives javascript error on any date selection. the javascript error is "Unable to get property '_selectedDates' of undefined or null reference".
It looks like it is destroying shared calendar object on partial postback.
Please find below sample code to replicate the issue. after clicking "Submit" button, it doesn't open calendar popup for "Date 2" and for "Date 1" it opens but doesn't allow to select date and gives JavaScript error.

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<asp:ScriptManager ID="sc1" runat="server" />
<telerik:RadCalendar ID="dtCal" runat="server" EnableMultiSelect="false" />
Date 1:
<telerik:RadDatePicker ID="dt1" Width="103px" runat="server" SharedCalendarID="dtCal" />
<hr />
<asp:UpdatePanel runat="server" ID="up">
	<ContentTemplate>
		Date 2:
		<telerik:RadDatePicker ID="dt2" Width="103px" runat="server" SharedCalendarID="dtCal" />
		<br />
		<asp:Button runat="server" ID="btnDT" Text="Submit" />
	</ContentTemplate>
</asp:UpdatePanel>
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When i add all controls in UpdatePanel it works properly. but Actual code is much more complex than above sample with too many lines of javascript code and many date pickers on single page and simply all Calendar and DatePicker controls can not be moved in UpdatePanel.