System: V+12 voltage in enclosure Internal is out of spec.

It could be that the circuitry that measures the voltage has an issue.  If that's the case, you can just ignore it or make a change in the configuration so that it stops reporting it.  Something could be dragging down the voltage, which would be irreparable.  

But the external supply is still the most likely candidate.  Have you tried another one?  

A droop in power brick's input power will not normally cause the output of the power brick to droop.  If it drooped far enough, it could shut down, but that would have re-booted your NAS.  If the connection to the NAS is loose, that could be an issue, but it would most likely need to be wiggled for the droop to occur.  A temporary high demand on the 12V power, like a failing hard drive, might cause a droop in the 12V.  Just because there are some for whom the typical fix did not work is not really a good reason not to try it, IMHO.  What matters is whether the investment in a replacement supply (12V, 5A with a  5.5mm x 2.5mm or 5.5mm x 2.1mm connector) is worth it to you if it doesn't work.  Given there are a coupe on Amazon right now for <$10 (assuming you are in the USA), it's not a bad investment for what is very likely to be the fix (again, IMHO).  I suspect you can find far more "yes, it was the power brick" responses to similar questions than ones where it was not.  But unfortunately, some for whom a fix we recommended works never come back to confirm it was.  But they do if it didn't fix it, because they want another option.  

Of course, with it not currently showing the error, it's not going to be obvious if you just saw an unusual glitch or if the replacement was necessary.  Then again, if that is the problem and you don't replace it, a future failure could corrupt your volume.

for sure its not a bad idea to spend $10 for a new brick to at least eliminate that possibility.  Thanks for that idea.

Are you aware of any command line cmds or utilities I can use to detect the current voltage?  I can't find it displayed anywhere in the frontview web interface...just logs from a few days ago.

Have you updated your Ultra to OS6, or are you still running 4.2.x?  If you are running OS6, you can install lm-sensors (apt install lm-sensors) and then the sensors command will tell you that and more.  Note that if you've not already changed your sources.list to point to the Debian archive, you'll have to do that first (see How-I-got-apt-update-and-install-to-work-with-Debian-Jessie).

If you are still on OS4.2.x, I can't help you there.

WARNING:  DO NOT run sensors-detect or make any other changes to the system.conf, as that will cause issues with the OS6 system monitoring.