When you're running for books from enchantment solution, you can receive just 'book',
The process will error and stop, and not proceed till you break and replace the lectern once manually to reset the villager.
Don't know, why villagers need to trade for just books, lol. But yeah, the stopping sucks.
It's actually quite simple, but this tag==null check is also kinda required - I will see what I can do
When you're running for books from enchantment solution, you can receive just 'book', The process will error and stop, and not proceed till you break and replace the lectern once manually to reset the villager.
Using v2.0.1 with mc 1.20.2