The same thing happened to me last week. The mast base rotated out of the mast when the 2 forward rivets tour out of the mast. The mast was deformed enough at the base that I had to saw off about 1" from the bottom of the mast and reattach the base. I used stainless rivets and west marine epoxy to secure it together. I have only used the boat once since, but all seems to be working just fine. Hope this helps, andrew.