External drives not appearing in Finder window on Sonoma

Hi

I had a problem that started months ago, still unresolved, that I believe began with Sonoma but that is not definitive, where some usb drives wouldn't appear in a Finder window's list of drives.

Last night, other drives, USB and SSD have stopped appearing in the Finder window's sidebar but still appear in a content column to the right—still attached pic.

See how Films 9a appears in the side bar, while 9a and 9b appear in the content column.

Any ideas what has caused it? It could be Sonoma, it could be my Mac mini.

I'd appreciate your help.

Royks

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