indeed!, all files and folders in the /config folder should be set to owner nobody group users, the ONLY exception to this is the supervisord.log files, which are written as root, as supervisor is running as root user.
im quite surprised it was file permissions in the end, as it still doesnt explain why it worked on the rollback to the previous version, that makes NO sense to me whatsoever! as you arent rolling back any files in /config, maybe the previous version doesnt need to write to the db and thus doesnt actually care its read only *shrug*.