So it turns out that the cause was indeed a rogue change they couldn't roll back as we had been speculating.
Weird that whatever this issue is didn't occur in their test environment before they deployed into Production. I wonder why that is.
All companies have a test environment. Some companies are lucky enough to have a separate environment for production.
It's as if they were running Windows 10 Home on their servers and had an upgrade forced onto them
Change Manager who approved this is gonna be sweating bullets lol
"Let's take a look at the change request. Now, see here, this section for Contingencies and Rollback process? Why is it blank?"
If this is how they do their routine updates, they have had an extremely lucky run so far. Inadequate understanding of what the update would/could do, inadequate testing prior to deployment, no rollback capability, no disaster recovery plan. Yeah nah, you can’t get that lucky for that long. Maybe they have cut budget or sacked the people who knew what they were doing? Let’s hope they learn from this.