I’ve just started getting lots of older notifications, from the past several days, they keep popping up like random. Is this happening to anyone else?
Yes. Some do not appear at all, and just in the last few minutes I received notifications that are from a day or two ago’s messages.
Yeah, happened for me too. Got a notification from something that was posted yesterday.
A few minutes before that the site took a long time to load and finally displayed an error message.
Okay, thanks all, give us a little time, we’ll sort it out. Technically speaking, something went wrong. 
From the meta.discourse forums this seems to have been a known issue in an update from last week. I’ve updated discourse again so hopefully the problem will go away.
Thanks so much.
And thanks for the detailed very technical description! Technology is a wonderful thing.