Interesting. I wouldn’t do any more factory resets, though, in most cases they don’t really help, and just erase any stored diagnostic data that might help Sonos figure out what is going on.
It may be worth submitting a system diagnostic, and calling Sonos Support to discuss it, or post the diagnostic number here for a Community Moderator to pick up.
There may be information included in the diagnostic that will help Sonos pinpoint the issue and help you find a solution. There might not be, too, I’m sure that not all parts of the device report data to the diagnostic. But it’s worth the phone call, either way.
When you speak directly to the phone folks, there are more options available beyond just the diagnostic analysis.