When the coroner first jumps into the water to check Mona's dead body, he is neck-deep in water. For the rest of the scene, he is dry from the waist up.
When Ellen leaves the gas station after hearing what happened to Phil, her gas cap is on top of her car. When she stops the car in the next scene, the gas cap is back in place.
Phil's shirt when he is looking in the mirror is dark; in the next scene at the funeral home it's a white striped shirt. Jeff's shirt appears to be a black button-down silk shirt with a green design, but at the funeral home he wears a regular black T-shirt with a band logo.
When everyone's gathering in front of Rona's and two policemen are stepping out of their car, Lucinda's pickup truck is behind then, but a few shots later Lucinda is just arriving.
When Rona and Phil meet in the cabin for the first time, the board game lying on the bed repeatedly changes position between shots.
Roman Catholic weddings are very rarely held outside a church. Father Tom is dressed in clerical street clothes; he should be wearing a surplice (a white garment over his clericals) and a stole (a long a long scarf-like strip), which are required when a priest administers a sacrament. Catholic ceremonies never ask for objections, as the proposed wedding is announced three Sundays prior. Finally, the priest does not "pronounce" the couple married. The bride and groom are sacramentally married when they finish exchanging vows; in essence, they marry themselves..
Jeff's car, with Mona driving, has no working brakes. When Mona backs out, we do not see brake lights come on, and the sound implies she uses the clutch to stop the car and go forward, thus never using the brakes.
When Mona attacks Bobby's car, Bobby and Jeff both appear to speak as Bobby gets back in the car but no sound comes out of their mouths.
When Chief Wyatt Rash gets into his car to check Bobby's alibi with Murph, camera is visible in car door reflection.
Mona drives into Hudson River. Clarence sees the accident from a covered bridge. However, when Wyatt questions him later on the bridge, it spans a pond or creek. The Hudson is nowhere in sight.
Occasional glimpses of palm trees in the background indicate that the film was shot in southern California rather than the story setting of New York State.