When a skeleton hits an arrow on the player, damage is normally dealt. But when the skeleton misses the arrow and passes close to the player, the arrow disappears and a noise of collected item rings (but no item has been collected). If I'm not mistaken this bug happens when he misses the arrow and it goes near the player. When a skeleton arrow is attached to the ground and the player passes over, the arrow disappears and a noise of collected item touches, but the arrow has not been collected.