I've just come across a bug when trying to rename paper in an anvil. I was trying to rename 64 items of Paper with the name 'Sorting'. I pressed the outgoing slot where the renamed paper would be and when clicking it the paper disappears and 1 xp is removed from my XP bar. However, I don't have the renamed paper and the stack is untouched (64 remaining).

If I relog the game I get my 1 xp back as if it never happened. I tried multiple times and still the same effect.

So I put 64 paper in, rename to Sorting or something else, took renamed paper out, paper disappears aswell as 1 xp, original stack of paper is untouched. Reloading gives me 1 xp back.

If you do single pieces of paper this works fine, it won't work with stacks.