NUC bug
From Jon's Wiki
Occasionally the NUC will crap out. There seems to be no rhyme nor reason to it, but dmesg is full of these:
[drm:gen8_irq_handler [i915]] *ERROR* The master control interrupt lied (SDE)!
And occasional dumps, like this and this. It's a 1.6 GHz Intel Core i5-5250U Broadwell, on Ubuntu 15.10 latest. There is a Launchpad bug, but I'm not sure that's helped, as I still get errors on the 4.2.0-17.21 generic kernel.