Chasing some gremlins out of my computer – there was a partial unplug event on the usb hub my monitors are connected into, and that messed up the firmware in them, so they were running constant disconnect / connect events for their built in card readers. This eventually crashed the USB bus.
Rebooting the computer didn’t solve it, but power cycling the displays did.
New battery for the UPS arrived.
Had my 8th Covid shot.