I would first perhaps power-cycle the speaker and setup the ocean waves track, to repeat a single song (or to replay the queue - whichever you require) and simply try again and see if that brings about success.

Did the Support tech comment on how long the One has been up and running? It sounds like it could have rebooted.

Thanks for the replies!
 

 I have both tried rebooting and repeating single tracks without change in problem state, unfortunately.

Finally, no, the support tech did not comment about uptime or bother to look at diagnostics though I have sent them.

As @ratty mentions the queue should not clear itself unless the device is rebooting, or it’s perhaps cleared by a user, or other 3rd-party App etc. So perhaps keep an eye on that.

I’ve just tried the Sonos single track replay function here on a Sonos One (stereo pair) using a song from Amazon Music and it seems to be working okay. 

Maybe try a different non-overlapping wireless channel (1, 6 or 11) and see if that makes any difference.

Thanks for the response, Ken.  

Here's my final bit of info concerning this issue: after the behavior occurs once, if I awake in the middle of the night and start a playlist again, on repeat, it will happily play as designed into the morning.  

So...I put my play:one back into commission, same wifi/playlist/power source, and...no such problem occurs.

As a result, I've repurposed my One as a theater surround.

Chalking it up to ghost in the machine though I still wish that support would have wanted to look at a diagnostic.

Thanks again.