Eject Device is not working

I do not know what changed, but Ejecting from calibre Device menu fails.

The device remains in connected mode, and when I try to use Finder to Eject, it says 'one or more programs may be using it'. Retry fails as well, so I'm left with Force Eject...

Quitting calibre and then trying to Eject with Finder also fails.

It's happening with both my Kobo Clara Colour and my Kindle Paperwhite (11th generation).

Sequoia 15.1, iMac 5K 27 inch 2020
calibre 7.21

I think this was happening with previous version of calibre (I updated today) and before macOS update I applied yesterday.

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Hmm. This has nothing to do with calibre: restarting macOS, mounting device and Ejecting isn't working.

Open to troubleshooting ideas!