Revealing mistake: Towards the end when the Phantom's lair is collapsing, you can see bricks falling into the sewer water and floating. Obviously they were made out of light-weight material and not out of actual stone.
Revealing mistake: When the officials arrive at the Talbot family tomb to investigate the recent events, they find the crypt door unlocked. As they start to enter, the door opens on its own. When the camera cuts to an angle from inside the crypt, a thick cord can be seen pulling the door open.