My librarians will not trade enchanted books to me. They have enchanted book trades that are already locked in, but when i select the enchanted book trade on the left (the trading options), the enchanted book will not show up in the output on the right. If the villager has other trades where i am giving the emeralds, those trade outputs will show up in the trade output slot. This happened to all of my librarians at the same time, immediately after i had returned home from the end. I have enough emeralds to do the trades that i am selecting and the villagers are fully stocked (there is NO red X) 

In the screenshot below, i am repetedly clicking on the highlighted trade (the enchanted book trade)