Yes, MyCloud restarts destroy Twonky settings. It’s due to the poor integration of Twonky into MyCloud.
I give some workarounds here:
http://community.wd.com/t5/WD-My-Cloud/FAQ-Twonky-DLNA-Media-Server-Setup-amp-Use/td-p/858810
Ideally, WD would do a better job of integration, but I see no willingness on their part to do this.
It’s also a good question to ask why the MyCloud restarts if internet connection is lost.
