Factual error: Raoul is the Vicomte de Chagny and he gets called that throughout the movie, even during the auction (which shows he didn't change titles when his parents or his brother died, for example). Yet Christine's tombstone calls her a countess when it should have read viscountess - or, even better, vicomtesse.
Trivia: When Christine removes the Phantom's mask, he pushes her down on the floor. Right after he says 'Curse you,' the camera goes back to her: she is half laughing. (00:45:30)
Suggested correction: She's not laughing, it's shock and fear, she doesn't know how to react.
Suggested correction: When you watch "love never dies" he leaves her because the phantom won the bet, it's implied they got a "divorce" so she is still a countess.
But, in love never dies, it shows Christine dying in the year 1910, (when the whole thing was set) but on her tombstone, it shows that she died in 1913. Since Gustave is ten years old, this would make Christine in her late forties-early fifties when she had him, which is practically impossible. This is why I love LND's music, but the story is just too cheesy and inconsistent to the original for me. Since the original creator of the musical, Andrew Lloyd Webber, has chosen to call it a "stand-alone piece." and not a sequel, I would not use it as a reference for future endeavors with the trio.
Vicomtesse and Comtesse are two completely different titles. For Christine to become a Comtesse, Raoul would have had to become a Comte, but he didn't. He remained a Vicomte, therefore, Christine's tombstone should have read Vicomtesse de Chagny. It doesn't, so this mistake is valid.