I am having this same issue, totally random, sometimes it works sometimes it doesn’t. Sometimes it will play fine and if I pause when I return to play I get the error. Symptoms started with the upgrade to S2, prior to that I never had issues. So frustrating. Also do not recommend airplay to the speaker from he stitcher app this is not stable and will not keep multiple speakers in sync.
I find in often works best when airplaying to just one speaker in the Airplay list and then grouping it with other ’rooms’ in the Sonos App - no sync issues when doing it that way round.
Unfortunately that’s not been my experience, I can get them all to play but then each one will randomly drop out of the group, sometimes they will rejoin the group, sometimes not. S2 has been thoroughly frustrating in my experience. Thanks for the suggestion though .
Sounds like you may have some slight Network interference - you may find this video helpful:
https://youtu.be/3fQAAL5IwTE
Appreciate the info but bear in mind this only happens with stitcher, all other music services work fine, Spotify, pandora, amazon music, calm, etc. only stitcher has these issues.