Thank you for contacting us.
I have examined your code and your AJAX settings look properly configured. I have created a simple project with one button opening RadWindow with user control in it. In the user control there are two buttons for adding and deleting data in a xml file (with client-side ajaxRequest), using your AJAX settings in the RadAjaxManager, which works fine on my side. Also in this case you need only one ajax setting which will indicate that the RadAjaxManager will update the Repeater. The updating of the datasource takes place in OnAjaxRequest server-side event.
Please take a look at the attached project and see if there are any differences from your logic and let us know if this helps you with your issue.
If you want to get updates on new releases, tips and tricks and sneak peeks at our product labs directly from the developers working on the RadControls for ASP.NET AJAX, subscribe to the blog feed