On the imported fbx you have to fix the avatar sometimes. Click the configure button and make sure the right bones are assigned correctly.

That's very odd, I had the exact same problem before and it was because the humanoid avatar had assigned several of the fingers incorrectly, such as the thumb where the pinky should be. So even though everything looked green on the avatar it was not correct. Click on the original fbx in your assets and look in the inspector  window. Do they look twisted there? What about if you have it set to generic?