Q: Title changes don't stick

In iBooks on the Mac, we now have the capability to change book title, collection, category, and author (at least for books that are not from the iBookstore and are DRM-free). Sometimes, however, when I change a title, after I quit iBooks, the old title has resurrected itself. This does not happen on all books, but always happens on certain books. The author, collection, and category can be changed without difficulty and stay changed (unless I try to delete the category entirely, in which case, if the author comes back, so does the category). How can I permanently change the ePub book title? Is it necessary for me to edit the ePub directly (