Plot hole: Spoilers. It's revealed that the barn game takes place at an old farmhouse owned by the family of Jill Tuck - Jigsaw's widow. It's public knowledge that she was married to Jigsaw and that buildings they owned served as the headquarters of several past traps, so the barn should have been investigated at some point in the meantime. Ten years have passed. It makes no sense that the barn was never investigated and that the bodies of the barn victims were never discovered.
Revealing mistake: During the opening trap, at one point one of the five "Bucket Heads" starts banging on the wall behind them. If you look very closely, you can see the set-wall waver slightly as it's struck, revealing it's not really a concrete wall. (And it's not supposed to be the doorway that is later revealed during the final twist. It's a separate section of wall). (00:05:40)
Suggested correction: No it's not the section that is a door, but that door does prove vital here. By showing the door, shows there is a section behind the wall. Meaning the wall we see is most likely a completely false wall and not the structural wall. With it being a false wall it is entire pleasurable that it could move.
When Jigsaw opens the door, you can see the walls are indeed solid and are at least 6-8 inches thick. Given the fact they appear to be made of concrete and run floor-to-ceiling, sorry... there's no way they are moving when someone bangs on them. Also, why would Jigsaw make a "false wall" that was so easy to move when someone hit it? He'd be setting himself up to possibly be caught. Sorry, but this particular correction is just too far-fetched. It's just a mistake.
Plot hole: An order is given for the body of John Kramer to be exhumed. Surely the police would have noticed someone had dug the grave up in the last few hours (days at a push) as Logan had to get Munsen's body into John's casket.
Plot hole: Jigsaw is apparently omniscient - he was able to correctly identify all the sins of his victims even though he couldn't possibly have been there when they occurred.
Suggested correction: As we have seen throughout the franchise, Jigsaw has several servants who prepare traps for him and such (known as "Pigheads"). They would have been present at the time.
I don't know about this; Carly, for example, stole a purse with $3.53 in it. There is no way even the Pigheads would know that amount or be able to connect it to the death of the woman she robbed. In addition, if they were there to witness that specific crime, they easily could've saved the woman too.
Revealing mistake: When Mitch's tape plays, if you look closely you can see the tape is not actually moving inside the recorder. (00:45:15)
Revealing mistake: At the beginning when the coroner cuts the bucket off the body, the metal is red hot and her pinky touches it. Not only does it not burn the glove but it doesn't burn her.
Suggested correction: The metal is not red hot, it was cut by a laser that gives off a small amount of smoke. Nothing says the metal is hot. So no burn is reasonable.
Your correction suggestion completely contradicts how laser-cutters work. The metal would definitely be hot if cut with a laser cutter. That's how laser cutters work - they essentially melt the material they're pointed at in a very controlled fashion, and they do indeed get quite hot.
Smoke doesn't make the metal glow red, that would be heat. Also for the laser to cut through thr metal it needs to heat it up.
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).
Continuity mistake: When Logan is shown the message found on the second victim, the string in the evidence bag attached to the note changes between the close up and the far shot. (00:28:30)
Continuity mistake: When Carly dies we see her fall down onto the right side of her face. Camera cuts to a close up of the blood pouring out of her ears and neck, and she is lay on the floor on her left side with her right side of her face upwards. (00:20:30)
Continuity mistake: The amount of blood on the memory card Logan finds changes between shots. (00:12:30)
Continuity mistake: At the start Edgar smashes his car up and kicks his window out and jumps out leaving a bit of glass in the window frame. However after the camera changes, the 2 bits of glass have disappeared. (00:01:05)
Audio problem: When Logan explains how Edgar killed Logan's wife, the camera is an over the shoulder shot looking at the cop. Logan's mouth isn't moving. (01:18:05)
Deliberate mistake: During his autopsy in Saw IV, it is revealed John Kramer was 52 at the time of his death. Kramer's role in this film is the very early stages of his time as Jigsaw, shortly after his cancer diagnosis, which would put him in his early 50's. However, he looks far too old to convincingly be that young (Tobin Bell was in his mid-70's at the time of filming). He even looks older than he did when he was on his deathbed in Saw III.
Other mistake: During the opening trap we see Mitch strike the blades with his chain and get yanked forward. However, despite being yanked forward he still manages to stand in line with the others which he shouldn't be able to do, as his chain was shorter due to the extra tug he received. (00:06:30)
Suggested correction: The chain is tugged by the saw blade catching it as it is going round, when it gives loose of the chain, the chain is not any shorter than the others, as the saw blade did the tug not the motor pulling the chain in.
Suggested correction: The game was unknown to police even 10 years after John died. Now they've found all his other games and his multiple lairs. There would be no need to continue the search.
Hogwash. They would have definitely searched known properties associated with Kramer and his family.
I agree. In the second Saw movie, the police discover that John Kramer is Jigsaw. With this knowledge, not only would the police be able to freeze his assets but, they would be able to look into his financial records and look into any properties he owns like houses, warehouses, etc. Since the cops now have a face and a name, it's a very big plot hole why they never searched his home or any other places. If they had, more traps would have been found and confiscated.