Things seem to work fine for me. You can find a short video attached that shows how this behaves on my end as a reference. There is some loss of framerate due to the screen recording softare, both in the played video and while dragging, but locally in all cases the video plays as expected and the lightweight mode moved more smoothly. Framerate also depends on the Internet connection and the played video itself.
Here is the code I used:
There should not be such issues because the lightweight render mode actually renders less and simpler markup that should be faster for the browser to render. It is very likely that the content is what is causing the slowdown. Could you test this with a blank RadWindow to see if there is a difference?
Nevertheless, if in your specific scenario you have issues with the lightweight mode you can simply keep using the Classic one.
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