Librarians can offer same book twice

Randomly caused ?
Does this affect one villager or multiple ?
Can you reproduce this ?

Very random, obviously the chances are low, even for the more common books. It has only happened once, although I regularly breed villagers and unlock their tiers - especially librarians. Again, because of the random percentages involved, I expect it to be quite some time before I reproduce it. I euthanised the villager in question, he had no books on offer that I didn't already have.

From what I know of the mechanics, it would only affect Librarians and their books, as that is the only item class that is capable of being offered multiple times on different tiers, ergo requires a specialised check just for this instance.

Random does what Random likes.

I have never reported a issue before but i was recently playing and when i started to level up my librarian villager it ended up have unbreaking 2 twice I was playing on 1.16.1

I was playing on 1.17, and I got a villager with two Bane of Arthropods books. Both books were of same level, and the only difference was that one costed more than the other. Especially irritating, as that particular enchantment is one of, if not my least favorite enchantment in the game. I even prefer curse of binding on a pumpkin to that! Curse of binding! On a pumpkin!

1.19.2.

Curse of Binding (固咒) twice in different price.

I have the other one who sells Smite twice, one is V, the other is II.