So, after carrying out some forensic investigation on what went wrong, it appears that our upgrade to a newer version of Redis didn't work. It looked like it had, but hadn't.
We've corrected the issue with Redis and everything appears to be _properly_ working now, but we'll monitor the situation.
Unfortunately because of the nature of the issue the @trumpet account didn't receive any of your messages saying there was a problem!
Apologies for any inconvenience caused folks 🙂