I suspect that multiple sound issues reported here are related, e.g. this one :
Xperia 10 III audio and video problems trigger after a period of time in use - #11 by elkiaer.
Today I received a sound notification about a incoming whisperfish message. The notification sound was coming from the speakers although I was listening to music via headphones. From this very moment on the music was played by the speakers and not the plugged headphones anymore. Neither replugging headphones nor the Audio Output Choser app (Audio Output Chooser | OpenRepos.net — Community Repository System) were able to change this sound from the speakers back to the headphones.
This happened multiple times the last days. In a more serious case all sound goes to some unknown sink and the media players are running very slowly, even regular phone calls are silent. But this extreme behaviour occurred only once to me.
In my case only a reboot restored normal audio behaviour and the working switch between different audio outputs.
In case I can contribute to provide some logs or similar I am happy to do so with some instructions what might be helpful