[Georgie W]

Nearly all the covers in one of my Calibre libraries have disappeared.

I have 2 libraries, one for e-books—all covers are present & correct.

The other library, for physical books, has a mixture of
* out of print books, where I've scanned in covers myself (and updated the edition info in GoodReads accordingly)
* books with existing covers in GR or Amazon, where the cover is automatically downloaded when I enter the book in Calibre.

Tonight, I've noticed that almost all the covers for the physical books have disappeared. Only covers I've created / downloaded in the last week or so are present.

ETA The "missing" cover images themselves are present in the relevant book folder—they're just not being picked up by Calibre for some reason.
E.g. Peter Ackroyd's "London Under", which I entered last week, has a cover visible in Calibre.
Peter Ackroyd's "Hawsmoor" (entered a year or so ago) has no visible cover, but I can see the cover jpg in the directory folder. [End of edit]

I've exited Calibre & restarted, I haven't updated it recently (ver 7.19), or made any changes. I have a back up of my Calibre user settings from a month ago. Is there anyway to bulk-restore the images for just the Physical Books library from that?

I know I can download only cover metadata but I have nearly 1,000 books, and I'm meticulous about getting the right cover image—the automatic download routine can be hit and miss on whether it gets the right cover. I'd rather avoid that chore if possible.

Any help welcomed. Thanks.