IIRC some Sonos issues are related to STP. AFAIK it's, like you said, Sonos being Sonos. Lol.

Yeah, that was exactly it. Unifi have a special page in their docs for dealing with Sonos.

https://help.ui.com/hc/en-us/articles/18930473041047-Best-Pr...

I ended up connecting everything with a wired connection and disabling WiFi. Thankfully I have cat6 to every room so it wasn't an inconvenience.

It's worked perfectly since.

How could a Sonos device possibly interact with spanning tree? Are there Sonos devices that act as bridges?

Most of their devices act as bridges; some of the newer ones don't. Some have multiple ethernet ports, and anything that has both an ethernet port and is part of their "sonosnet" mutant-wifi will bridge between sonosnet and their ethernet port(s) with spanning tree using classic (pre-RSTP) link costs.

If you're not careful you can end up with the "best" path between two switches going over the sonos-to-sonos wifi.

That’s nutty!