You can open a support ticket where you can send us a sample. Note that actual logic and datasource are not needed, just the layout, a dummy datasource (e.g., a List or array, created in a simple loop) would suffice. Note that the RadWindow declaration and the way you open it will also be needed.
In the meantime I would advise that you review your layout in a simple page outside of a RadWindow, once that works as expected with the size you use for RadWindow, put the page in an iframe with that size. Once that works as expected, things should be fine withing a RadWindow as well.
In order to open a support ticket you will need a valid subsription. For assistance with a purchase you can contact our sales team via sales (at) telerik _(dot)_ com.
On the subject of a live session - this is usually a last resort measure if we cannot work with any other code. Details on that are available here
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