iMac spontaneously shuts down after installing Cp 2019 update (11.0.1.266) OSX 10.13.6

It's a hard crash. The only way to get the computer back up is to unplug it from the surge protector and reboot.  It's random, but started after the update.  No message when it crashes.  I have no idea if it is a kernel panic.

Apple says it could be related to a specific program.  If your Mac spontaneously restarts or displays a message that it restarted or shut down because of a problem - Apple Sup…  

Has anyone else experienced this?  I've replaced the surge protector, ran diagnostics (no issues found), and thought if anyone else had this issue, I could start trying to isolate the cause. 

My next step is dragging the beast to the Apple Store for a new power supply.

Thanks!

Alice