Hi JKC,
I had some issues with my mast step before too - a 1/4" crack in the fiberglass, visible under the panel by the head.
I had it repaired at the yard. They found a void under the step - it looked like it used to be filled with an epoxy that had broken down due to repeated compression from the mast punching down when going through waves. They built up the area under the step with G10 so it's solid now.
