I had this same issue where it kept overwriting. I then decided to delete it and re-enter it. Then I started to get the hit a snag message. I spent 2 hours with someone in chat with no help! Eventually I found another thread to figure out a resolution on my own. Instead of deleting it from this screen, you have to go to tools and then forms. Then look for the 1099-SA and delete it. Then you will have to re-enter it, but it allowed me to add a second one after that.
