I kept experimenting further and found the problem. DuckDuckGo App Tracking Blocking has been enabled on my phone for a long time already, without problems. But suddenly DDG started acting up, blocking internet traffic to the Pandora App and AlphaPlayer (SomaFM) while phone is locked.  Once I set DDG battery usage from Optimized (default for all apps) to Unrestricted, both music apps resumed working like the used to in the past. FYI. The Pandora App is sadly leading the list of blocked tracking requests. ... View more