Based on the various comments from various threads it does not appear to be. That is one of their oldest AZ's so I would lean towards automation that probably

Based on the various comments from various threads it does not appear to be. That is one of their oldest AZ's so I would lean towards automation that probably worked in all the other AZ's maybe stepped on some old technical-debt-landmines. Maybe they will post a post-mortem given the impact. Hopefully people go easy on whoever tripped over that bug/landmine.