Asterisk needs SERIOUS TLC under Xenial, Holy crap.
Asterisk as configured under Xenial install is in a very broken state, as seen by this log:
http://paste.ubuntu.com/24609099/
Problems were discovered after looking at the pluto logs, specifically the Asterisk device.
Problems exist on both i386 and amd64 builds for Xenial.
More discovery needed to formulate a comprehensive solution.