Problem(s) Encountered:

...about 22:30, we realized the detector had warmed up.  Went downstairs to do a nitrogen fill.  Don't know the cause, but perhaps it was operator error in the dewar fills.

We saw the temperature start to fall, but then Owl became unresponsive.  We restarted it, and got error messages during the Setup phase -  not connected to any device.  

Solution:

Reboot mdmarc2, perhaps too quickly as I noticed a ds9 window disappear when the system reboot.  This indicates that another version of Owl was already running (and likely connected).  After the reboot, no further issues.
As for the dewar warming up, thankfully I have good vacuum on the Observatory detectors.  Standard protocol, if a dewar is left to warm up, is to allow it to completely warm up.  Observatory staff would then pump the detector and perform the initial cooldown and tests.