It appears there is some javascript/Vaadin code that is resizing the page editor iframe on page load. In the presence of a touch-capable monitor, somehow on Chrome it is making an incorrect guess that the device is a tablet and setting the iframe height to something very large, which makes it impossible for the user to see the bottom of the page. No other browsers exhibit the behavior.

For these users, editing becomes impossible and we have to advise them to change browsers. Chrome is otherwise our recommended browser so this is problematic.