(at around 5 mins) When Louis is checking on Ellie after she fell off the tire swing he is wearing a tee shirt without a collar and sleeves that are rolled up midway past his elbow. When Rachel gets up to rush after Gage his tee shirt is now an open shirt with stripes and a collar. In the next shot when he gets up to follow Rachel his shirt is once again back to a tee shirt.
(at around 1h 25 mins) When Louis falls out of bed, he hits his head on a nightstand, dragging a pillow off the bed when he falls. The pillow is shown very clearly on the floor between the bed and the nightstand. A few shots later the pillow is back on the bed again.
(at around 43 mins) Distance between Ellie and Louis as they talk about Missy changes between shots. In the close-up, they are side by side, as we see them from the kitchen, there is distance between them.
(at around 5 mins) When Louis is checking on Ellie after she fell off the tire swing his pant legs are down. When Rachel gets up to rush after Gage his pants legs are now rolled up. When he gets up to follow Rachel his pants legs are once again down.
(at around 5 mins) When the family first arrives and Gage walks to the back of the station wagon to see their cat Church, his bowl is on the right side of the carrier in front of him. In the next shot of Church in the carrier (immediately after they show Gage's face looking at him), the bowl is on the left side, behind the cat.
In the beginning when the family asks about the trail to the woods it is shown as a bare footpath. In later day shots it becomes sparsely lined with dull river rocks, and at night it shows a denser line of different, reflective stones.
(at around 47 mins) Just before Gage gets hit by the Orinco gas truck, it is shown leaving the depot and driving down Route 15. The black-and-white badge emblem on the highway sign identifies it as a US Highway. However, US Route 15 runs between New York State and South Carolina. This film is set in the state of Maine. (In the book, the road is Maine State Route 15.)
(at around 49 mins) Gage ran out in front of a tanker truck that was displaying a "Dangerous" placard. On a tanker the placard would be the type product being hauled (i.e. "Flammable", "Corrosive" etc). The "Dangerous placard is reserved for mixed hazardous materials. You don't mix on a tanker.
(at around 57 mins) When Bill Baterman is looking at his son Timmy's Purple Heart, the enclosed ribbon and lapel pin in the case are for a completely different medal. The ribbon should be identical to the cloth portion of the Purple Heart.
(at around 41 mins) When Missy hangs herself, she is dangling from the back of her shoulders, instead of from the neck. A metal shackle can be seen at the end of the rope. No doubt part of the harness supporting her.
(at around 1h 21 mins) When Jud is attacked by Gage with scalpel neither wound inflicted bleeds. You would expect there to be some blood on the scalpel when Gage is shown holding it between the heel and face slices given how deep the blade went into Jud's heel but it's spotless.
In the outdoor scenes where Louis is alone on Thanksgiving weekend, the trees in the background have leaves on them. (As they do in subsequent scenes.) In Maine at Thanksgiving time, the trees would have been bare.
Louis torches Jud's house in the morning, and the ruins are still burning after nightfall. No firefighters are present. If the firefighters had been there, they would have easily determined the fire was arson, and there would have been a long investigation involving the police, yet there are no policemen and not even any crime scene tape. In any case, the firefighters would not have left without putting out the fire completely. This means the fire was allowed to burn all day long. The smoke would have been visible for miles. Louis and Jud were not the only people living in town, and there was an endless parade of truckers on Route 15. Did not even one person ever call the authorities?
When Jud is first showing the Creeds the "Pet Sematary" Jud tells Ellie that his dog Spot died of old age. He later tells Louis that Spot died because he got caught in barbed wire and got infected. This is actually an important plot point. The dog died of gangrene, the young Jud resurrected him, and a few years later the dog died again of old age.