After documenting the issue below, I rebooted the affected Sonos units and the problem was resolved. Unfortunately, it appears to be another case of (Sonos) updates are the enemy. If it ain't broke, don't fix it/don't update. I'm posting the info below in case someone else experiences the same/related issue.
I have a few Rules that use the 'Speak on Sonos' Action. Randomly all announcements began repeating, endlessly:
Attention, this is a test
Attention, this is a test
Attention, this is a test
...
Both Sonos and Hubitat are running the latest available updates. The Sonos zone is not grouped and Sonos Repeat is not enabled.
I created a separate rule to test:
The issue exists irregardless of the 'text-to-speech' or music-player choice:
After discovering the issue only occurs on three of our seven Sonos zones I though it may be caused by a Sonos update and only affecting certain hardware but that doesn't appear to be the case:
