After reloading the page, the content is displayed correctly. However, the page seems not to stop loading content from the server.

The first time the page is loaded, the "blank" page with a grey background is loaded into the editor, but the content (with a white background) never replaces it. That would indicate there's a problem in loading the content to the editor.

If wiki markup is the default mode, the markup editor displays fine, and you can switch to the rich text editor with no problems.

A workaround is to reload the page after the first load, or to make wiki markup the default.

Might be related to CONF-4808. We will need to test whether upgrading solved this issue.