When the carriage arrives for Christine, Raoul & Gustave, they're shown walking away from it. In the next shot, they're looking at it as Gangle greets them.
The show is consistently stated to take place 10 years after the previous musical. However, despite the original story taking place in 1881, Love Never Dies is stated to take place in 1907. Therefore, if Gustave is actually The Phantom's child, he would be 26 years old.
During 'Gustave! Gustave!' Gustave says, 'Please Miss Giry I want to go back!' but his mouth doesn't move. The shot is from the scene afterwards when Meg takes him to the pier to drown him before the confrontation, while the other scene is in Coney while Christine & the Phantom are looking for him.
Some scenes have two facial microphones posted on the left side of the Phantom's face, while in other scenes only one microphone is visible.