The Bug occurs if you are adding or altering makros in WYSWYG-fullscreen mode and afterwards leafing the fullscreen mode. Then the editor area has the same size like in fullscreen mode but is embedded in its scroll pane. That means that you see just the viewport clip of the editor area (see screenshot 'bug.png'). Additionally (and thats the bug) you have a horizontal scroll (see screenshot 'bugscroll.png')
the normal state (entering edit mode) of the editor window fits into the upper panel (see screenshot 'bugright.png')).
this bug is existing at least since version 2.4 and on every browser.