Minecraft version 1.12.2, mod version 1.7.1

1. When placing an enchanted Mjolnir on the ground, the enchantments are lost upon picking it up again.
2. When dropping Mjolnir through an End portal from the overworld, entering the End causes unrecoverable world files in singleplayer and corrupted region files in multiplayer.

Fixed both with the respective commits:
d2d3142
f4be60c

Just an FYI I completely disabled enchanting Mjolnir, as originally intended.