In the denouement scene in the arsenal, while standing near the safe, Christine begins wearing a rain coat which then becomes a fuzzy cloth coat.
When Christine runs into the Arsenal to burn the paperwork, she's wearing flat shoes. Inside the Arsenal, she's wearing the high-heeled pumps that she'd been wearing in the immediately preceding scene; in other arsenal sequences the style of her shoes also changes from one scene to another.
When O'Malley rings the bell at the Forrest entrance gate; there are five guard dogs that start barking while rushing to the gate then the gatekeeper walks out. But on the next cut when the gatekeeper walks directly to O'Malley; the dogs have now disappeared and there is no barking. The gatekeeper never said or did anything to make the dogs go away or to stop barking. Then on the following cut after the gatekeeper has left; the dogs are now back at the gate again.
Just before O'Malley is threatened by Geoff, his hat is wet. Immediately afterward, his hat is dry.
When O'Malley uses Geoffrey's car to drive to the Arsenal; he leaves it parked on the main road near the path to the Arsenal. But on the following cut when Geoffrey and three others are driving in another car down the same road toward the Arsenal; the car driven by O'Malley is not there when they arrive.
When the taxi driver crashes into the doctor's parked car at the front of the Forrest entrance gate; the doctor is at the gate preparing to leave and there are also two guard dogs with him. The crash caused a loud sound but the guard dogs did not react. In reality, the dogs would have started barking or at the least have been startled by the noise.
The damage to the doctor's car by the taxi driver is very minimal. However, if you take into account the speed of the taxi and the sound of the crash the damage should have been significantly much more.
When O'Malley buys a football at the general store; the clerk tells him that the cost is a dollar and a quarter then O'Malley hands her a bill of an unknown value. But when she rings up the sale; the cash register reads $5.20 and she gives him change in bills and coins. She only rang up the register once so she could have only entered the sale price or the amount of money he handed her. In either case, it is a mistake. Also, he could only hand her a five or a ten or a twenty-dollar bill; therefore even if the $5.20 represented change it would still be a mistake.
Correction: the amount on the cash register when O'Malley buys the football is backwards to the customer - not $5.20 but $1.25. Keys pressed were for $1, .20 and .05.
(at around 43 mins) When O'Malley asks Jeb where his sister is now, we hear Jeb answering, but his mouth doesn't move.
When the newspaper articles are shown near the end of the movie, the first name in O'Malley's bylines changes between Steven and Stephen.
When the Arsenal is on fire, Christine uses the phone to call for help but to no avail. She then stops trying to get a signal and tells O'Malley that the phone doesn't work. O'Malley then informs her that Kerndon had cut the lines but despite the aforementioned, she resumes trying to get a signal.
When Jason Rickards is escorting O'Malley out; he tells him he will get his car. However, O'Malley doesn't have a car. He came in a taxi which was waiting for him at the gate.