I'm certain there's probably a dedicated bug reporting facility, but i could find it.

The bug: some times the fullscreen view does not take up it's inital size/space when returning to non-fullscreen view. The issue is a result of position:absolute not being removed from the containing div and/or sizes not being applied correctly.

steps to replicate:

1. load up a wysiwyg editor 
2. click on preview view
3. click on code view
4. click the full screen button (repeat to see the issue better)

 you can produce a similar issue (possibly the same) by completing the following steps:

1. load up a wysiwyg editor
2. click on code view
3. go full screen
4. click on preview view
5. click to remove fullscreen. 

many thanks,

Dan 

edit: I've managed to follow the error down to the offending method: 

this.AttachFrame(); used in editor.js (and possibly this.DetachFrame();)  unfortunately i cannot diagnose these methods properly.