Oddly, stations can change their URLs. Try deleting the current alarm, then set up a new one, and see if the next time it ‘alarms’, it grabs the right ‘station’. 

I have this exact issue. Have deleted and recreated alarms to no avail. As a retired software engineer, I have to say I can’t believe Sonos can’t get this simple task right. Very frustrating!

Same problem here, as well as playing a previously-chosen station instead of the one clearly selected on the app screen. It’s as if the app issues a PLAY command before it selects the chosen station. Work on app reliability, SONOS, not on adding new “functionality”. And allow us to choose the Now Playing screen as the default screen to show.

My alarm has recently chosen to play the chime instead of the selected station.  Annoying and why?  
 

So far only for the alarm using a tune in station and it’s started after I had to set up the new tune in service. No problem with the previous tune in service. 

This new one makes it much harder to find a specific station 

Usually, when the chime sounds, rather than the programmed station, it’s an indication that, at the moment of the alarm, the speaker is unable to reach out across the network and access the required stream. All sorts of possibilities around that, from local network issues, all the way to the server from the streaming company being overwhelmed with requests, and not being able to respond in timely manner.
 

Try pushing your alarm forward 2 minutes. Or set up a new alarm, as the URL in use may have changed, and you’re getting lost in a translation matrix. Or submit a diagnostic with 10 minutes of the chime, and call Sonos and ask them why the chime, and not the station. 

That’s interesting.  My daily alarm except for Saturday is for bbc radio 4 which is not via tune in service. It works fine 

Saturday morning alarm is for wnyc am and has to be thru the tune in service. Since the new tune in was forced on us this has happened several times. 
 

I have deleted and reset the bbc alarm for next week. I will now move back the time a few minutes. 
 

Thanks for your reply. 

Unfortunately, radio stations change URLs fairly frequently, and streaming services like TuneIn rely on look up tables to do the hard work of transferring data back and forth as transparently as possible. I know Sonos can be impatient, especially on alarms (better to wake you with a chime than miss the alarm while they’re trying to find the station). I suspect your resetting up the alarm will help.
 

It’s possible, for instance, that the station had moved from streaming company A to streaming company B in the background, and while you wouldn’t normally be aware of that, it’s showing up on your alarms.