As far as we can determine from the screenshot, one of the three editors you have is in fullscreen mode, yet it is unable to render on top of another editor that you have on the page.
Taking into account the way ToggleScreenMode works, this could happen when you have absolutely positioned elements on the page. Is this the case in your scenario? If that is so, is it possible to change your layout to not use absolute positioning?
In case you believe the problem might be somewhere else, one thing that will be helpful would be to open up a support ticket and send us a HTML page dump for us to examine further.
the Telerik team
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