Found on Quark Pack (Version 97)
While using an AFK fisher, I had two enchanted fishing rods in my hot bar. When one of the rods breaks, both of the rods disappear. It eats an item if it's replacing a tool and you only have two left as far as I can tell. Having 3 or more pickaxes for example doesn't trigger the bug If i recall correctly.

I believe the root cause of this problem is the same as #485