I can’t now find it here but someone mentioned the BA problem as possibly a network router one. I was involved in a high integrity centre where part of it crashed despite its very high integrity on paper and very competent engineering team.
It wasn’t due to servers, main software or power but something that affected both main and standby routers. Although there had been the odd glitch on these in service everyone thought it was insignificant as it quickly recovered until that day. Ultimately no one could replicate the problem off line and so the real cause was never really discovered. The only solution was to replace the routers with a different type.