Put the summary of the bug you're having here

What I expected to happen was...:
I was trying to use 28 emeralds to go to a Librarian villager and buy a Mending book

What actually happened was...:
When I clicked on the trade, the other trade filled in.  The other trade was 9 emeralds for a bookcase.  I bought it, tried again (with the correct amount of emeralds) and no matter what trade I click, it only lets me do the trade for a bookcase.  I tried on a different villager who sold a Piercing 1 book.  It would not let me buy the book either - only the other trade for a bookcase

Steps to Reproduce:
1. Find a librarian villager who has two trades - one for an enchanted book, and one for a bookcase
2.  Click on the trade for the book while having the correct number of emeralds
3.  See if it fills in the correct trade before accepting