Librarian villagers can sell the same book twice

The bug

Villagers can sell the same enchanted book twice, at different prices.

How to reproduce

Seed: -8435927518894423097

Coordinates: /tp -4942 67 2267

Trade with the librarian villager inside the house. The last two trades are both a Silk Touch book, one for 16 and one for 17 emeralds.