The bug

When creating a new world, the enchantment seed defaults to 0. When loading an XpSeed with value 0, it will be randomized, probably because the game assumes it hasn't been initialized yet. This is a problem in the following two ways:

• If your enchantment seed is set to 0 randomly, it will change again once you reload the world. Admittedly, this is a rare occurrence, but it should be mentioned.
• The enchantment seed changes when you reload the world for the first time.

How to reproduce

1. Create a new world in creative mode
2. Place an enchantment table and put a book in it. Do not enchant it, but do take note of the enchantments that are shown when hovering over the 3 slots.
3. Save and quit to title
4. Reload the world
5. Place the book in the enchantment table again and do enchant it this time
6. Observe how the enchantments you receive (likely) do not include the ones you were promised in step 2.