Hi,
Whilst syncing downloaded Audiobooks from my mac mini M4 pro running macOS 27 to my iPhone 18 Pro Max running iOS 27 I spotted that the audiobook covers are not displaying correctly on my iPhone within the Books app. The same audiobooks display correctly on the Books app on my mac mini though.
All Audiobooks seem to take the cover art of the same two audiobooks (they alternate between the two covers).
UPDATE: the same symptoms are also being seen whilst syncing music to the Music app on my iPhone.