Unenchanting on a grindstone leaves original enchantments

When using a grindstone to disenchant a bow, XP is earned but the original bow remains enchanted.

Original description:
I’m unable to craft a bow at all. I’m trying to complete the dispenser achievement. Once I get the 3 string and 3 sticks, and craft the item, the materials leave my inventory, but no bow is placed in my now empty inventory. When disenchanting one of my previous bows on a grindstone, it becomes stuck in the grindstone and becomes an exploit for gaining xp as it gives you xp for disenchanting it, However it still has all of them on the bow.