The bug
Anvils and other falling_block
entities with HurtEntities
set to 1b
kill items and xp orbs.
How to reproduce
Make a tower of anvils
Place a non-full block, 2 blocks beneath the bottom anvil
Remove the block in between the non-full block and the anvil
→ ❌ The anvils kill the already dropped anvil items resulting in a single anvil item in the end
Can confirm for Minecraft 1.12.1. Only the last anvil is left.
What I did notice though, is that when an anvil falls on a torch, the torch disappears and the anvil remains. The torch didn't seem to drop its item, which is probably because it was "crushed" by the anvil.