Character mistake: Early in the film, Sister Paxton reveals that she wants to come back as a butterfly after she dies. Reincarnation is not a tenet of Mormonism.
Character mistake: The official in charge of announcing the voting results keeps pronouncing Cardinal Adeyemi's name in different ways; he puts the accent on the last "e" the first time, then the French way on the last "i", then mere seconds later the "e" again. Considering Adeyemi already walked in the conclave as one of the 4 favourites, and that utmost care was put in the preparation of the ceremonial (in an earlier scene, Ralph Fiennes' character makes sure he knows how to pronounce the name of one of the unimportant cardinals), it's quite the egregious mistake that he keeps repeating. (00:44:20 - 00:44:50)
Character mistake: Characters frequently refer to there being crocodiles living in the water. Alligators live in Florida, not crocodiles. And although they are closely related, they are not the same species.