Mac is ejecting external drives randomly

Be sure you check the box to never put drive to sleep when display is off in energy saver pane and test

If they are both going off at the same time I would suspect

cable(s)

if attached to a dock, the dock or dock cable to the Mac.

USB-C connector’s physical connection to the Mac. I’ve seen them become loose and not hold well.

Power. Put everything on an Uninterruptible Power Supply (UPS). I had a co-worker that kept loosing network connections. Put the modem and router on a UPS and the problem stopped, but every so often the UPS would beep that it had lost power. Turns out there was a bad household wall outlet.

You may also want to try another cable as I have found with Monterey that connections are very finicky. I went through 3 cables before I had a robust connection.