This seems to happen enough that many at our field have replaced the "stock" rod or long bolt with a heavy threaded rod available from a good hardware store. The replacement can be thicker and will hold up better. You will drill through the threaded end of the cap, use two nuts to lock it on there. Use a nuts on the front end also. In addition I was just told to mushroom the ends of the rod to prevent the nuts from coming off.
I'm off to the hardware store right now!!