System simply returns "Killed" (ref.: http://community.wd.com/t5/WD-My-Cloud/Firmware-04-00-00-607-running-btsync-or-unison-instantly/m-p/767995/highlight/true#M18314, 4th paragraph first post). It's thus likely per design by WD but there´s a reference to rebuilding Debian packages to resolve it (ref.:http://community.wd.com/t5/WD-My-Cloud/New-Release-WD-My-Cloud-Firmware-Release-4-00-00-607-7-9-14/td-p/761150 under Important Note:). Running btsync and other 3rd party stuff has thus worked well until the latest fw upgrade. Myself I have rolled back to earlier fw and can not make the tests just now.