Since 18w22a, every time I log out and log back in to my minecraft world, all my enchanted books have their enchantments converted to protection. I tried a number of styles of logging out:

Saving and quitting to title, then returning to the world without closing minecraft- Only enchanted books in my inventory retain their enchantments.

Saving and quitting to title, then returning after closing down minecraft- Only enchanted books in my inventory retain their enchantments.

Closing minecraft without returning to the title page, then returning- all enchantments converted to protection.

I haven't tested this with ender chests yet.

The attached screenshot shows an enchanted book wiped by the glitch. I can't remember all the original enchantments, but it contained thorns 3, fire aspect 2, respiration 3, and projectile protection 3. (I was saving it for an ultimate helmet)

As a side note, (this should probably be a separate issue, but I don't have the time to test it too) all dropped items disappear on logging out and logging back in- I'm not sure under exactly what conditions.

This glitch is game breaking- please fix it! If anyone else has additional information concerning the causes and conditions of the enchantment losses, please comment.