I was playing in my world after upgrading from 1.12.2 to 1.13-pre3 and I looked at an enchanted book and it didn't show the enchantments - also happened with villager trades.
I did a bit more testing and it seems to be easy to repeat with worlds upgrading from 1.12.2 to 1.13-pre3.
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is duplicated by 3
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Most likely caused by 1.12.2 using numerical enchantment IDs, while 1.13 replaced them with string identifiers. 1.13 doesn't understand what "enchantment ID 3" is anymore, it only understands things like "enchantment ID 'minecraft:blast_protection'" instead.
A fixer/walker needs to be added to convert these IDs in 1.13 for worlds coming from previous versions.
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