Would you please replace the RadWindow with a standard IFRAME element and check whether the problem persists? In case it does, apply the needed settings to remove it and after that apply the same logic to the RadWindow.
In case the problem is not present with the IFRAME which is configured as the RadWindow, please open a new support ticket and send me both pages and I will make the one which contains the RadWindow look as the one with the IFRAME.
the Telerik team
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