Anvil disappear after fixing an item

(Excuse my english, I'm not an english native speaker!)

It is the second time that my anvil disappear when I fix an item (this time it was a stone sword with 3 enchantment that I've fix with stone).

The first time there was a block just above the anvil. I tought that it was the problem. But the second time there was only a torch above the anvil (there is a block on the left and and the right of the anvil).
I get the repaired sword in my inventory, but the anvil totally disappear.

This bug cost iron!