Repeat NUT corruption?

[DownloadDeviant]

Hello all,

I had this problem before and chalked it up to a fluke back in July 2017, but it happened again exactly as before this morning so I'm seeking some guidance now. My stats are in my signature.

NOTE:
NUT was properly configured and has been working reliably for a year now. I've even experience 5 or 6 real world tests and it shut down properly during storm outages a few times. My UPS is directly connected to my Synology DS415+ Diskstation(remote UPS/NUT server) and the pfSense router is a client. I've made no changes other than updating from 2.4.3 to 2.4.3p1 recently. Everything else has been untouched for months. I have NOT reinstalled NUT at this point either. Waiting for feedback.

In short -
My pfSense router shutdown by itself this morning. No power outage or fluctuations. I had to reinstall 2.4.3 and recover via Pre-Flight Install with a matching 2.4.3 config file. All my hardware tests fine, even the CyberPower UPS.

Like in July, a reinstall & recovery from a clean config backup file didn't work. It just immediately shutdown again. I had to search for and REMOVE all references to the NUT package. This is how I solved the problem before so it was not as terrible an experience this time around.

I have no logs because...reinstall. The only thing I have are these email notifications prior to me noticing the router was off.
Wed, 20 Jun 2018 09:37:42 -0400
UPS ups@192.168.79.155 on battery
Wed, 20 Jun 2018 09:37:47 -0400
UPS ups@192.168.79.155 on line power
Wed, 20 Jun 2018 09:38:12 -0400
Auto logout and shutdown proceeding
Wed, 20 Jun 2018 09:38:12 -0400
UPS ups@192.168.79.155: forced shutdown in progress

What I think could be possible causes:
NUT update went bad?
Communication glitch between Synology and pfSense/NUT?
NUT became confused, thought UPS was on battery, shutdown and got 'stuck' believing UPS was on battery and should shutdown.

I want to understand what is happening so I can learn and I'd like to prevent this sort of thing from happening again.

Thanks for any and all assistance.