Factual error: 6 years in a mask and he's able to keep that lovely babyface with just a little bit of grime, which easily comes off? Of course it would have wrecked the whole story but still...

Audio problem: In the Bastille dungeon just after Phillippe knocked out the guard with the key we hear Athos say 'We feared the mask would destroy you', but his lips do not move in sync with this. It looks more like he originally said 'We thought you were dead'.

Continuity: In the scene where the Jesuit tries to kill King Louis, Louis grabs a long bladed knife and stabs the Jesuit in the chest, but when the camera pulls back, the knife is gone, and no one has made a move to pull it out of his chest. Only the blade that D'Artanian threw at him is there.

Continuity: The mask that is removed from Leo has 3 parts - a face mask which is held onto Leo's head, with a 2 piece hinged cage that locks in the back. In the flashback, where they show Leo being put in the mask, it is only 2 pieces. The face part is fused to the hinged cage section.

Audio problem: At the mask-ball, when Louis is seeing iron masks everywhere and rushes out, the music suddenly stops, but in the background we can see the violinists still playing (moving their bows) - we don't hear any sound.

Visible crew/equipment: In the very first scene, the boom mike's very obvious at the top of the screen.