Mutiplayer: Repairing Tools with an Anvil doesn't work

When you try to repair in anvil with the base material(example: Iron Helmet with Iron Ingot) the item isn't repaired, the anvil return you the base material, the item and you lose exp.

STEPS TO REPRODUCE:
1.insert a tool and the items to repair it
2.shift+right click or left click to repaired item (the anvil reset and you loses exp)

I think is an important bug, please repair it.
Thanks for read it
------------------------------------------------------------------------------------------------------
I FINDED THE REAL PROBLEM:
The anvil say you an experience cost (example, 3lvl) but the sistem use more experience (example, 12lvl).
I finded it when i tried to repair a iron pants with other iron pants. The anvil say me "experience cost 1" but when I repaired it, it used more than 10lvl.

I want make a video soon.