An Alexa outage appears to have been my problem. Alexa commands for light groups were solid for weeks. Suddenly this morning any Echo in the house I used would state 'A few things share...Which one did you want?' After a couple of hours things are stable again.
What's more interesting is I've been having the issue where Alexa would trigger my light group on/off command correctly but then state it's not responding.
That also appears to have self-corrected (for now).
