Carved Bookshelf bag

When I fill the Carved Bookshelf with books - both enchanted and regular ones - and then make a copy of it along with its contents using the Ctrl+scroll mouse combination, the copied bookshelf appears empty when placed. However, when I destroy the copied bookshelf, the books I previously placed in the original one fall out. Interestingly, if I click on any book in the copied bookshelf, the previously copied books will also become visible.