They recently pushed out an iOS update for Messenger that crashed to springboard any time you tried to resume it from background. It took a couple of hours to get a new build up, plus however long for affected users to all install the new version.
I'd love to hear the story of how that made it through testing.
Sorry, should have just said "home screen" for clarity, but SpringBoard is the iOS application that makes the home screen. It's akin to Finder.
A fresh launch of Messenger worked until you switched out and put it in the background. When you tried to resume it (either from home icon or task switcher) it would immediately die and could be launched fresh on the second try.
Basically every time you wanted to use it you either had to kill it in the app switcher and then launch it, or launch it twice.
My favorite part is that since Facebook doesn't do useful release notes (best guess because they're testing different features on different users and changes never actually land for everyone in a specific version), all the App Store said for the busted version was "We update the app regularly to make it better for you!" Oooops.
Though that's an interesting thought, I wonder if a feature had rolled out to a subset of users and it was crashing because it tried to pull some piece of account info that doesn't exist on accounts without it? Testing still should have caught that, but if the test accounts were all testing the new feature I could see it sneaking through. From my end it looked like a 100% reproducible crash on resume which is pretty sad to release.
It's the same for all sites beyond a certain size. It's never fully up. It's very rarely fully down. It's gradually degraded in ways that you hopefully don't see, but sometimes do. Or maybe you don't see it, but others do. etc etc etc. Availability isn't boolean once you have users.
