Got this on one of my machines yesterday - haven't seen that particular error message before from stderr

My other machine also crashed a task about the same time. with the following stderr output
Signal 3 received, exiting...
08:35:32 (1760): called boinc_finish
Controller:: CPDN process is not running, exiting, bRetVal = 1, checkPID=0, selfPID=1732, iMonCtr=2
Model crash detected, will try to restart...
Leaving CPDN_Main::Monitor...
08:35:59 (1732): called boinc_finish
both with lots of suspend requests first.

Two things in common.
1. Both machines upgraded to latest xubuntu so kernel has gone from 3.x.x to 4.x.x
Secondly at some point yesterday there was a momentary brown out where the lights dimmed for a fraction of a second. I am guessing that is the most likely explanation for the first one on this machine but would have thought the laptop battery would have acted as a ups?