I believe I may have discovered a bug which, as far as I can tell hasn’t been reported yet, but I can reproduce over and over:
I have two Sonos One SLs. I can successfully pair these two speakers to become a stereo pair, and I can play to this set perfectly fine from within the Sonos 2 apps on both my iPhone and MacBook. However, if I try to play a song from within Apple’s “Music” app using AirPlay it breaks the stereo pairing - one of the two speakers stops playing music altogether.
It then remains like this regardless of the music source or whether it’s being played from the Sonos 2 App or Music App (via AirPlay). It does not split the two speakers into separate rooms, sound just stops playing out of one of the speakers. I can fix this by using the “Remove Stereo Pair” option, which then does separate the speakers into two rooms and each works fine again, separately.
I can then re-pair the speakers, and it will all work fine again until I attempt to start an AirPlay session to them like before, which triggers the same cycle repeatedly.