I discovered the exact same problem with the same mast piece for my 6270 Forbidden Island. In this set, the twisted notches prevent the brown mast rigging / rope net pieces from connecting properly to a base plate. I kept thinking I was crazy or missing something. I also wondered if the twisted notches were a feature intended to give sails in ship sets an expressive turn to the side. I discovered the problem in my own set just a couple days after you posted here. Funny timing!