Jessie implies that you are using default that I cannot name for fear
of starting a flamewar. But it hasn't been heavily tested in
conjuction with NIS/yp.
I have worked in an environment that dynamically set the hostname
based upon dhcp name. That was quite the nightmare in many ways
because machine dhcp239 would report a failing component. Where is
it? What does it do? Who's system is it? Things were much better
after the dynamic naming was abandoned and static naming was resumed.
I avoid dynamically named systems except in special circumstances.
Although that is not your current problem. Obviously you like it that
way or you wouldn't have done it that way.
I would reconfigure /etc/network/interfaces for "auto" and restart.
Once an interface is configured in /e/n/interfaces then NetworkManager
should ignore that interface from then on. I am hoping that will be
enough to solve your issue.