Audiobooks are not showing up in Apple books app on the iphone IOS 17.5.1

I just drag and drop some books to the iphone part of itunes (connected to a PC as I did since I got an iphone, all the books are .m4b) and some of then appear without a problem on the app and some don't, I did the following

1. close and open the app again (no luck)
2. boot the iphone (no luck)
3. delete all the audiobooks from the itunes screen and reinstall everything the app (no luck)
4. I move only book 2 of a 3 book saga, and it shows without a problem, move book 1 and 3 and book 2 disappears.

Is there a way to reset only the audiobook data base? it looks something is corrupted there, or is there a way to solve this without resetting the phone.

Thanks in advance.

Carlos

PS: any good audiobook app to replace this one??