A lot of QA, especially at the system level, is just luck. That’s why it’s so important to dogfood internally imho.

And by internally I don’t just mean the development team, but anyone and everyone at the company who is allowed to have access to early builds.

There's "something that requires highly specific conditions managed to slip past QA" and then there's "our update brought down literally everyone using the software". This isn't a matter of bad luck.