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The first instance I created stopped updating and refused to work with simple methods suggested on the net.
I created a whole new instance on the second day and deleted the persistent dir so I have no data to work with for troubleshooting.
The probable cause where the YouTube RSS feeds that seem to be producing errors like 404 and 500.
docker volume inspect freshrss-data sudo ls /var/lib/docker/volumes/freshrss-data/_data/
docker logs -f freshrss
docker exec -it freshrss sh
ls /var/www/FreshRSS/