Editing in Google Chrome squishes edit area at top of screen

The page displays correctly until attempting to edit when the editable area is squished to the top of the window. This can easily be observed in the attached screenshot where the scrollbar for the editable portion only covers the top 1/3 of the screen.

This issue is less than 1 week old.. Confluence has not been updated and no plugin or configuration changes have been made in that time.

Classified as 'Major' as editing is unreasonably difficult under these conditions.