OS X client crashing computer when logged out

Had this happen twice now: I've played the game for a while, then logged out (all the way out to the login screen), and left the computer. Come back to find it hard crashed, all the way back to a reboot. ('SotA' shows up in upper left of main screen on restart, which seems to be SotA/Unity's 'I dunnit' signature, as verified by the OS' startup message as well.)

This is not the OS X 10.14 problem, as I am on 10.12.6. The problem appeared first in R64, doesn't seem specific to a particular patch, so probably related to Unity version change.