If you remove the repeat-track function, does it then play all the way through? …and what is its actual running time? Have you tried the same thing with a different track from the same/different source?

It always plays the track once in full, then starts skipping back after 15 seconds or so from then on. The precise amount of “play” time varies depending on what track is being played. All the tracks I’ve tried it with have full track times of between 3min and 7min. I’ve tried various tracks from difference sources. 
Normally I appreciate this wouldn’t be a problem unless you REALLY like a song, but in this instance it’s playing sort of white noise to sleep to. 

The streaming audio that a device plays is buffered and if the buffer empties, the player skips to the next track. In this case the repeat-track feature is ‘ON’ so it’s repeating the track and so the problem repeats - that’s at least what I think is happening here.

The next question is finding the reason why? …and so my first suggestion is to simply begin by trying a different ‘fixed’ non-overlapping 2.4Ghz Wifi channel on your router (use either channel 1, 6 or 11), that’s assuming you are running your devices on your WiFi and have no devices wired to the LAN/router. Also set your channel width for that band to 20MHz only. A reboot of the router and player is also worth doing. Ensure no other wireless devices are near the speaker aswell.

If your system is running on SonosNet (with any Sonos product wired) then ensure the SonosNet channel is set at least 5 channels away from the chosen router channel. 

See if that then resolves your issue.

Thanks Ken… weird it’s not been a problem up until now, but I’ll definitely give all this a try

I’ve tried the above (it’s all run using WiFi). No change to symptoms. I have some extra intel though. I tried playing the exact same tracks using Spotify app connect bypassing the Sonos app (which is up to date) and it doesn’t suffer the same problem… it plays perfectly over and over ?

In that case perhaps try a Sonos App reset in “Setting/App Preferences” and after closing/reopening the App, choose the option to connect back to the “existing” system  and see if that sorts it. 

Did you reboot the Speaker/Router ?

One further quick thought… as you are initiating playback using an Alarm, perhaps delete the Alarm and see if setting it up again direct from the source (not from a My Sonos tab shortcut) solves the issue. 

Hi @Alexcawthorne 

Welcome to the Sonos Community!

What happens if you play the same track, on repeat, from within the Sonos app? If you get the same behaviour as with the alarm, please try removing Spotify from your Sonos system and add it back on again:

Remove a music service account from Sonos

Add a music service to Sonos

If you haven’t done so already, I also recommend your reboot your router by switching it off for at least 30 seconds.

Also happens to me, plays through first round and then when it repeats; it only plays up to 18seconds then it repeats from start. I have tried different Channels already. I do not think it is an interference issue as if I play it from SPOTIFY app it works OK. 

This only happened recently,  I definitely know this because my kid uses SONOS to repeat 1 bedtime story every night.

Agent I spoke to eve suggested to connect via WIRED/LAN… speechless as the main thing about this system is it being wireless...

Might be this, see response from SONOS STAFF: