I can add to my original post the possibility that this is Bluetooth related - when troubleshooting I kept finding postings that made changes to Bluetooth, such as purging cache, deleting and remaking the Bluetooth connection, and others. I tried those things without success. but I have since noticed that, if I power off my Bluetooth earbuds, the phone remains silent for a period of time - maybe 30 minutes - and then suddenly Pandora starts playing through the phone speaker! I attribute that to a persisting Bluetooth connection for that period of time - once the phone gives up on the connection and sound reverts to the speaker, then Pandora again starts to play. I have not made any changes to my phone or earbuds or Bluetooth for a year or more, and so I am inclined to attribute this to a software update - could be Android, Bluetooth drivers, earbud drivers or Pandora app. I don't have control over any of this, so I chose the patience option - post my problem, and hope that down the road some other driver / software update will come through and fix the problem.
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