Sebastian Stan filmed Avengers: Doomsday without ever getting the whole puzzle
Sebastian Stan is definitely in Avengers: Doomsday. He is apparently a considerably less useful source on what Avengers: Doomsday actually does. Asked about the movie by Le Journal du Dimanche, Stan said he never received the full screenplay and instead shot disconnected pieces of it. For Marvel, ignorance has one extremely convenient production benefit: it is difficult to leak a plot connection nobody told you about.