It sounds like bluetooth has 2 audio modes, one bandpass filtered (not completely as terrible as telephone quality) and one that is music worthy, and that Microsoft Teams for Linux likes to switch to the worst of them without switching back.
How can I debug what's going on here, to figure out if this is a bug in Microsoft Teams or Pulseaudio? Or better, how to correct it? Pavucontrol doesn't seem to expose this state.
What I know: If I want to listen to music inbetween calls, it doesn't help to reconnect the bluetooth headset unless I quit or restart Microsoft Teams first.
If it matters, I'm using OpenSuse Tumbleweed.
I always have pavucontrol open when switching between Teams and Spotify. The right-most tab "Configuration" has a profile setting for each output device.
Still, this is very annoying.