Audio problem: Anthony Hopkins is in his car with Cogman, discussing Pangea the super continent over the phone with John Turturro. There are two instances in this scene in which Anthony Hopkins' voice has been dubbed over by a different actor that does not sound like him. Anthony Hopkins first says "That's Pangea. The super continent." The scene then flashes back to the round table and the dubbed voice attempting to sound like Hopkins says "It's the same shape on the round table." The dubbed voice is heard again when he says "Genius", before reverting back to Anthony Hopkins immediately after when he says "Stonehenge."
Audio problem: When Halloran and Hunt are discussing orders from the commissioner to exhume Jigsaw, it's clear that several of Halloran's lines have been looped in post. His voice is a bit too loud and a bit more forceful than he appears to be speaking, and at least one word doesn't quite line up with his mouth movements. It can be hard to spot the first time, but if you look for it, it's noticeable. (Confirmed in DVD/Blu-Ray commentary - the actor lost his voice and his lines had to be looped).
Audio problem: When Rob starts accusing Benny of knowing what happened to him the previous night, Benny says that they just hung out and Rob says "Shut yo ass up" to Benny. The shot is focusing on Benny, with the camera behind Rob and his jaw does not move when he is saying the line. (00:56:20)
Audio problem: There are American crows (Corvus brachyrhynchos) calling in the distance during the initial pursuit for Quan in the forest behind the Belfast farmhouse, right after the trap door scene ends and we see two of Hennessy's men share a look. American crows do not exist in Ireland - only hooded crows, carrion crows, rooks, ravens and choughs.
Audio problem: Just after K finds the 6 10 21 marking on Sapper Morton's tree, he begins to head back to his car. In the shot from behind K where he is first walking to the car, the only sounds heard in the shot are his footsteps and nothing else. The shot then cuts to an angle behind the car with the door opening, and it is now shown that K has set Sapper's house on fire, and the sound effects of the flames burning are suddenly heard. The sound of the flames burning the house should have still been heard in the shot where K was walking up to his car as the house was already on fire. (00:49:15)
Audio problem: When Caesar and his companions come over to the lone soldier by the huts, carrying firewood, he puts the wood down and grabs for his gun. The sound of automatic fire is heard as he is shot, but when Caesar (the shooter) comes into view, he is carrying a pump-action shotgun.
Audio problem: At the Democratic National Convention when the female secret service agent announces that there is an active shooter, before firing her weapon, her audio briefly switches to sounding as if it were coming through as a PA announcement to the arena. Even though she's speaking into her walkie-talkie.
Audio problem: When John and another bodyguard/hitman are walking in a crowded subway/train station, and they're shooting at each other with suppressed 9mm or 45 ACP handguns across swaths of people and the people not reacting is an absurdity. High caliber handguns meaning anything larger than a .22 still makes a loud noise when suppressed. People in a general vicinity could still hear a noise and a pop. The only truly silent handgun is a .22 and it still makes a noise when the slide reciprocates back and forth. (01:18:00 - 01:18:45)
Audio problem: During "This is me", when they enter the room and get to the "oooh oh oh" part if you watch the albino the sync is out as their mouths open after the music has ended on that part.
Audio problem: After Adam and Noah finish talking about Chester Hills, the movie shows a few shots of the desolate land and bad conditions. One shot is a close up of a decaying dead cow, and in this shot you hear the loud sounds of flies and bugs swarming it as you'd expect on a dead animal. However it is just the added sound effect as there is not one single fly or insect visible. (00:09:35)
Audio problem: When Richard is running around the house trying to find Jen near the end, he is heard ferociously breathing and grunting. The breaths and grunts appear to have been dubbed in as Richard's facial and chest movements remain mostly still, which wouldn't happen if he was breathing and grunting that heavily. (01:41:10)