Minecraft: 1.16.1
Forge: 32.0.108
morevanillalib-1.16.1-1.2.8
vanillahammers-1.16.1-2.1.1

When breaking a shulker box with a hammer you lose all its contents.

Happens with every container that keeps its contents when broken that have pickaxe as their associated tool, there aren't any others like that in vanilla minecraft, but happens with containers from other mods that match that criteria. ("Portable Grid" from "Refined Storage" and "Compacting Drawers" from "Storage Drawers" for example)