Other mistake: Macrinus and one of his high-ranking friends are discussing Lucilla's son, who disappeared when Commodus died. The guy says that Lucius disappeared when he was "about 12," but in the original Gladiator, he was barely about to turn 8. They also say these events happened 16 years prior, but, again according to the movie lore (without even looking at history), he died in 180 AD, and this movie is set in 200 AD.
Gladiator II (2024)
1 other mistake
Directed by: Ridley Scott
Starring: Denzel Washington, Connie Nielsen, Pedro Pascal
Factual error: After the naval battle, Thraex is waiting for an informant who tips him off about Lucilla and Marcus Acacius's plans. And of course, as a well-educated gentleman of 200 AD, he kills time by reading the newspaper. Wait, what? Needless to say (to anyone but Ridley Scott, probably), ancient Romans wouldn't/couldn't exactly get their news by newspaper, the press having not been invented yet. This one looks so modern in its layout it even has headlines and a proper publication title, "Roma Viridia."
Emperor Geta: The gods have SPOKEN!