Thanks for the reply, Bob. Manually deleting core/cache and viewing in Incognito mode still produces the Console log error above.
To navigate to the Articles, we’re going Resource tree → click on Articles container page, clcik ‘Edit’ on a page from the Articles list.
Another strange thing is that when editing an individual articles page, there’s normally just ‘Article Title’, ‘Summary’ & ‘Content’ editable fields on the first tab. Since the update, we now also have the ‘Description’ field too.