There is a cutscene before you even reach the top of the temple which then wraps up the game. After dealing with the cultists on the first island, I was in no mood to shoot my way through them again. I did a mad dash past most of them straight to the cutscene, then my game crashed. So I had to do it again. Good thing it was fun both times

I did miss a checkpoint since I initially approached from the north. I had to get in my boat and hit that before the mission marker moved to the temple at the eastern tip of the island. So double check that.