An application code change released this morning changed the expected request for saving content changes with our API. This created an error where the content editor could still load existing content, and our users could edit content in their browser, but the changes weren't saved after the user left the item, or closed their browser tab.
We reacted to a spike in error rate and our engineers quickly found and resolved the problem in the code base. Unfortunately, the code that is in place to catch and report errors and log these failures wasn't set up quite correctly to catch all particular errors. This has also now been resolved.
We are very sorry to report that it is likely that any changes made during this outage will have been lost (except for the case where users haven't yet closed their browser or "disconnected" from our content editor). We take looking after your content seriously and have proactively taken steps to prevent these issues happening again in the future.