So my power went out today (thanks, AT&T!) and just like last time, as soon as the "running on backup power" dialog popped up, my Mac Studio was basically frozen. Moving the mouse took 20+ seconds to update its position. Once the screen locked, it could not register typed characters fast enough for the unlock dialog to not time out!

I unplugged USB from the UPS and rebooted, and it behaved the same at the login screen with no apps running.

Now, last time this happened, the next day I tested it, by unplugging my UPS from the wall -- and the Mac behaved perfectly fine! ◀◀ Read that part again.

It's not even under high load; the UPS said I had like 40 minutes of runtime left.

Once the power finally came back on, suddenly the Mac was behaving perfectly normally again.

Any ideas? For I would like my computer to function on backup power in the future. That would be nice.

Previously.