I have a similar problem and the "e.sender.destroy();" does not work for me.
Please see other thread https://www.telerik.com/forums/bug-window-open-removes-vertical-scroll-bar-of-calling-page#PtD0oeKl3E6fkhw5sSRdIw
Hope you can help.
A work-a-round for me is to set width and height to almost 100% and center window.
Thanks in advance.