Enchanted Books used in Grindstone won't be stackable with other books.

What I expected to happen was...:
I expected to disenchant the books and stack them with my other books.

What actually happened was...:
They were displayed as two different stacks. They cannot fuse into one. It's like trying to stack wood and stone. They won't stack.

Steps to Reproduce:
1. Disenchant Enchanted books in Grindstone.
2. Try to stack them with normal books you already had.