I spent around 3 hours trying to get a villager to trade me an unbreaking 3 book, when i finally got my villager to offer unbreaking 3 I traded him some paper for an emerald so he would keep his trades but upon arriving via minecart back at home with the villager I saw him change his profession to a toolsmith, when I tried trading with him after that, the villager remembered that I traded with him but he was now offering level 2 toolsmith trades, not my level 2 librarian I had. I noticed that in 2020 this was a bug too and the forum said it was "resolved" but I am still having this problem.