When Shack is talking to his teammate about the Everclear, you can see several people dancing at the rave in the background. But when Jason starts chasing him, they appear to be very far away in the cornfield.
Jason is skewered on the spikes of re-bar, and yet when he is hit several times from behind with the swinging vat, the ones coming out of his chest bend all over the place. In later shots, they are shown to be quite solid and sticking out straight.
When Jason throws Freddy against the wall, you can see that there is a large space between the window of the cabin and the end of the wall on the right. In the next shot where Jason starts to put Freddy through the window, you can clearly see that there is hardly any space between the window and the end of the wall.
When the girls are at Lori's, just after Kia asks them if they think she needs a nose job, the lights flicker. When they flicker Kia is holding a compact in her left hand and she begins to close it. Both hands are up by her face but then the angle changes to a wider shot and her left hand is empty and on her lap and the compact is in her right hand as she places it on the sofa.
When Lori explains she haven't had much sleep lately, Kia says "Lori, you had to sleep at the police station.". If you look at Kia's purse straps you can see some of Kia's dress sticking up between the straps. When it cuts, the piece of her dress no longer sticks up between the straps.
When Mark is telling about Freddy to Lori we see her holding her ears, then as Will appear, she takes her hands off her ears and lower her hands. When it cuts back to her she is still holding her ears, then she lower her hands again.
At the institution when they find the coma patients, Will picks up some papers from the patient's charts. The way Will holds the papers differs in the shot when Lori says "Who would do this to people?"
At school when Lori approaches Will, she puts her hand on his chin. Will then places his hand on Lori's hand and says "I thought you might be in trouble," while their hands still are on his chin. When it cuts, their hands are suddenly down.
In the end of the movie when Jason comes through the water stabbing Freddy with his own glove, you can see the spikes only coming out of Jason's chest. When it cuts to Freddy falling to his knees, the whole fist and parts of his arm-wrist suddenly has gone through his chest.
When the teens enter the mental institution to get the dream suppressant drug, it shows a security guard drawing his pistol in alert to an intruder banging on a door. The next shot cuts to show the response of two teens hearing a single shot fired, and then cuts back to show the security guard under the door with four big dents from Jason and two bullet holes. The holes are located at the top right hand corner of the door and the other near the door handle.
Out at the party when Kia comes to Will and Lori and says, "Let's go shake our ass on the dance floor," you see Linderman standing a few feet away from Will. When it cuts, Linderman is suddenly close to Will handing him a beer.
In one scene a security guard gets squashed by a door. It then pans over the door, and you can see large gray marks in the door, from where it's been bashed in by Jason. The dents are quite different from when the camera pans over the door, to the wide shot.
When the teen tranquilizes Jason and gets cut in half, we see the two parts of the body in the left side of the hallway. After a few scenes, when the camera gets a close-up of the body parts, we see one in the left side of the hallway and the other one in the right side.
During the final fight scene, on the dock, between Freddy and Jason, Jason pulls off Freddy's left arm. But when Lori and Will blow up the dock, the bodies of both men that go flying through the air have two arms.
When Kia is sitting on the couch with Lori and Blake in the beginning of the movie, Blake asks Lori, "So, Lori. Am I going to get that grand tour, or what?" Kia is eating when Lori is telling Blake to get the beers. But in the next shot, when Blake gets off the couch, Kia is smiling at Blake, and then goes back to eating.
When Jason and Freddy are at Crystal Lake, Freddy begins to make torpedoes fly at Jason. When he gets hit, he is right in front of the tank, and beside the ramp. But when he looks up at Freddy, he is about two feet away from the ramp.
When Jason is being attacked by Freddy on the dock, Jason is facing Freddy in one shot. But in the next shot, he is bending over, and facing away from Freddy. Freddy then hits Jason with the machete on the back of his legs.
In the corn field scene where Jason first catches fire after breaking one of the kid's neck. He chases Billy Bob on fire but his blade is clearly not on fire. Every time after that the blade is shown on fire.
When Lori wakes up in the police station and follows the dropping blood, she turns a corner because she hears a little crying. Right after she turns the corner, the cameras show office windows. You can see someone sitting down and a camera on his knees.
When the kid wakes up and his father is sitting beside him with his neck chopped on the porch of his house, the kid hears a noise in the bushes. As he walks towards them, we get a shot of the bushes moving - to the right of the bushes, the shadow of someone shaking them is visible.
It has been established through previous films in both series that Springwood is a town in Ohio, and Camp Crystal Lake is somewhere in or around Wessex County, New Jersey. The van sequence, therefore, would take up to at least 7 hours if we were to say generously that Springwood was on the Eastern-most side of Ohio and Camp Crystal Lake was on the Southwestern-most side of New Jersey. Even then it's already been a long night, between the massacre in the corn field and the break-in at Weston Hills. Unless Will was driving the van at a constant rate of 100 mph through the hilly roads of Pennsylvania, it seems unlikely they would reach Camp Crystal Lake before dawn, much less still in the middle of the night.
During the party in the corn field, the guy who Jason kills second (throwing his machete at whilst it's on fire)is running towards camera. The shot before you see the machete, you can see the actor is running with his mouth closed, holding something in it - the blood he spits out in the next scene.
When they are searching for Hypnocil on the Internet, we see a picture of the Hypnocil bottle reading "Hypnocil, 500mg, 1000 tab". We also see Hypnocil pills lying beside the bottle. Considering the size of the pills, the bottle could never contain 1000 pills. Not even close to 100 pills.
When the drug "Hypnocil" is researched on the Internet, an article about the drug appears. If you read the article, you can see that it has nothing to do with Hypnocil. The article is about drug testing of students who engage in extracurricular activities.
As Shack is running towards the camera in slow-motion, you can tell that he is holding a mouthful of blood, ready to spit it when he is hit by the machete. When he does spit blood, it splatters onto the camera in the lower right-hand corner.
When Linderman dashes at Jason and impales him with an American flag, Will is dragging Lori (who is supposed to be unconscious). He's dragging Lori by her arms. But when he suddenly reaches behind his back with his right arm, her right arm stays up in the air.
Several times during the movie Freddy's sweater lifts up to reveal either normal, unburnt skin, or a tight black undershirt. For example, when Freddy is hanging upside down from the large construction vat.
After Jason has killed Stubbs, we see all the kids in the room looking for Hypnocil. Then we see Stubbs being 'thrown' through the door. However, we can see the stunt double come running before going through the door. So he isn't actually thrown.
In the fight scene at the pier, after Freddy and Jason get thrown into the air by the carriage that smacks into them, they land on the pier in sort of slow motion. As Jason lands, you can see a kneepad.
In the cabin fight scene while Jason is trying to free his machete from the table, Kia picks up a wrench and starts hitting him. When she hits him across the face, you can see the wrench bend in her hand.
When Will and Lori are sitting in the van, the camera shows rain starting to fall in front of the headlights. But when the camera tilts up, there is a noticeable pause before the rain starts coming down on the windshield.
When Jason sends Kia's body flying into the tree during the fight scene at Crystal Lake, you can see the dummy's arm go flying off of the dummy, in the upward direction, in the shot after the body makes contact with the tree.