From the AJAX settings screen (/admin/settings.php?section=ajax) you can modify various parameters regarding how Moodle loads the YUI libraries. One of the options is to cache the JavaScript output. This has obvious performance benefits and should normally be enabled. However, during a recent update it appears that caching has broken the ability to edit. Whenever an editing page loads the browser throws the following error:

TypeError: M.core_formchangechecker is undefined

The form actually loads but because of the JavaScript error the rendering of the forum stops before it is complete, leaving the user unable to edit a number of options for the component being edited.

To work around the issue I have disabled caching. This isn’t ideal, but until a solution is found it is the most workable option.