[Valen Tine]

There’s two issues I’ve noticed.

The first is where the book cover is immediately replaced with a generic upon sideloading due to a bug. This one can be fixed in Calibre by disconnecting and reconnecting.

The second is where the Kindle is phoning home and asking for a cover on sideloaded books, presumably not caring that the book already has one, but maybe only if the book has an amazon: or mobi-asin: identifier in metadata. If the identifier matches with a book on the Kindle Store, it replaces your cover with that one. If it has one, but it’s incorrect, it just removes your cover altogether and replaces it with a generic. I’m thinking Kindle wouldn’t phone home about books with no identifier, but haven’t tested it. (Sorry this is vague, it’s something I realized today when I was trying to figure out why a cover was randomly disappearing but -not- due to the bug that Calibre fixes, sometimes happening hours later.)