Such behavior is not expected and should not come out-of-the-box from the Kendo Window.
The only reason I can think of for something like that to happen is that the window loads a view that also carries those assets. When the response from such a view is parsed by the browser, the browser will initiate requests for them and it is often that they will return with a "not modified".
If this view is in an iframe, that would be normal, expected, and necessary, because the iframe creates its own context and the Kendo widgets inside will need those assets. If you are fetching a view with AJAX to place its contents on the current page, you must remove those assets from that view. They must be added only once.
If this does not help you resolve this, I will need you to send me a small runnable example that showcases the problem in the Kendo Window so I can examine it.
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