When the editor is wrapped inside a fixed size parent with overflow:y: scroll, the "Toggle Full Screen" command (F11) does not make the Editor occupy the whole view port. The issue can be reproduced in IE. video: http://screencast.com/t/0pWlWAgKX1qD
We were not able to reproduce the issue with the current version of Telerik UI for ASP.NET AJAX(R2 2016).