And it’s entirely possible that it wasn’t a software issue either. It could be a hardware issue, that was “solved” by moving it, like a poorly connected wire, for instance. 

Yes, I bet it’s frustrating. But if, at the moment you dealt with Sonos’ CS, it wasn’t working, and they could see no way to make it work, there’s not much they’re going to be able to do. I’m happy for you that it’s now working, but I’d be willing to bet that it will fail again in the future, be it with a heat issue, or whatever caused it to fail in the first place.

There has not been a litany of other people who have been complaining about SUB failures on these forums, which would lead me to believe that the failure is specific to your particular situation, and not a software issue. Otherwise, I’d think that there would be dozens of other posts, or one of my two SUBs would have failed, too, and I’d be in the same boat. 

It’s possible that a wire moved on a speaker that never moved except during diagnosis.

It’s more likely that it was a software issue on Sonos side.  Hence the speaker working AFTER the software update.

Litany is such a subjective word.  There are many people with the same issue.