You mention in your first post you had issues with routines. Those never run locally, FYI. Smart lighting can run locally, but it depends on which devices are involved in the automation you create.
AFAIK they haven’t explained what happened.
For at least some issues they do, see link below. I’m not a programmer or any kind of IT professional so the details of stuff like that doesn’t interest me, and it’s possible they have posted their analyses of other incidents in the past too, I’m not sure.