I have had this problem also since last year. Enough that I didn't even consider it was my new UPS causing problems. I paid to have my 27" 2019 retina 5K also.
So I had asked and someone said the iMac is a workhorse and the UPS likes to take breaks and it was causing my iMac to freeze and reboot itself. Mind you I also had more outlets and hired electric company to add in more electricity to my house.
My UPS is from Costco and I purchased a new one from last year as I thought maybe it was my old UPS (same brand but older).
Now I have my iMac plugged into the wall and not UPS. My old 27" that I upgraded and gave to my dad never had one problem with the UPS. So it is for sure something to do with Mac.
I redid my desk area since I painted. Now I am plugging in my external harddrives to the UPS and both connected to the back of my iMac and guess what? It froze and restarted. I unplugged both external harddrives and it restarted with no problems.
Seriously I have ZERO idea why it's doing this!
So I had asked and someone said the iMac is a workhorse and the UPS likes to take breaks and it was causing my iMac to freeze and reboot itself. Mind you I also had more outlets and hired electric company to add in more electricity to my house.
My UPS is from Costco and I purchased a new one from last year as I thought maybe it was my old UPS (same brand but older).
Now I have my iMac plugged into the wall and not UPS. My old 27" that I upgraded and gave to my dad never had one problem with the UPS. So it is for sure something to do with Mac.
I redid my desk area since I painted. Now I am plugging in my external harddrives to the UPS and both connected to the back of my iMac and guess what? It froze and restarted. I unplugged both external harddrives and it restarted with no problems.
Seriously I have ZERO idea why it's doing this!