Kluson style tuners with cast back covers sometimes come loose from the base. I've seen them installed on Gibsons and Martins among others. The back cover is peened onto the base, meaning there are posts that go through a hole and then they are punched or hammered in a way that makes the post mushroom and that holds it in place. Over time they can loosen and sometimes fall apart. I use a spring loaded center punch and a small anvil to repair this problem.