Villager Librarian offers Efficiency V and another Unbreaking III book, when trying to buy the one of the two desired books, from either of the two effected librarians they will give you Aqua Affinity and the other Depth Strider I instead. When removing it from the trading interface it at first appears to be a right book, but when moved it turns into a wrong book.
This is has happened both on single player and continues when same world get loaded on a server.
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We're tracking this issue in MC-209286, so this ticket is being resolved and linked as a duplicate.
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