Never had this problem, you could try the following command in the terminal: devel-su chown -R radio:radio /var/lib/ofono
Getting the same error, you could stop the bt-sleep script and restart it after your BT connection is no longer needed. To disable the bt-sleep script run: devel-su systemctl stop bt-sleep-monitor.service to stop the script and devel-su systemctl start bt-sleep-monitor.service to start the script. Or you could try some of the BT on/off apps from openrepos. Maybe you need to disable the bt-sleep-monitor service to get these apps running, never tested this myself.
Cable or BT headphones?