Vaadin modal/non-modal subwindows issue with CKEditor component

I am hoping someone will be able to see this issue and point me in the right direction of what might be wrong so we can fix it (or report it as a bug to Vaadin if that’s the case). We are using Vaadin 6.8.8.

We have found that CKEditor’s MAXIMIZE feature (which takes over the screen and restores it when clicked again) works fine when the component is in the main window.

We have found that it works fine if a modal subwindow.

We have found that it works fine if a non-modal subwindow, but only if the window is moved before maximized.

But if it’s a non-modal subwindow, and you don’t move that subwindow first, maximize works, but when restored, the subwindow is grayed out (like it’s lost the focus and can’t regain it). If you refresh the browser, that subwindow is fully functional again.

This YouTube video shows it:
https://www.youtube.com/watch?v=PrGcGe1sdBo

CKEditor by default uses a z-index of 10000. On a subwindow, we set it to 11000 since it’s rendering on top of other editors in our main window.

You can reproduce the issue using our demo app at
http://open.esignforms.com/VaadinCKEditor/

I am experiencing the exact same issue with a modal window. Does anyone know what the solution is?