I found the laser status screen indicating the "WARNINGS" had triggered.  Went to the diode room to investigate.  Found "NPRO switchoff during run"
illuminated.

I reset the laser, everything returned to normal.  I have to look up what the error message means as I do not recall what it was for.  There is
no evidence of the NPRO dropping out over the past 48 hours.  Attached is the trend data for the past month.  No signs of the NPRO tripping out.

Maybe a glitch set it off, or either the insertion of the reference cavity heater card or the outer loop power stabilisation card.  Will check
again on Tuesday to see if the condition crops up again.