When Billy Pratt and Angel are having dinner, Billy opens a bottle of champagne that sprays out and douses one of the candles on the table. In the very next shot, Billy has his hand over the mouth of the bottle to stop the spray and the candle is lit. The candle is then out again, then lit again, then out a third time in following shots.
Inside the cabin, Sam hasn't quite finished buttoning Michelle's blouse when George enters. Later, the blouse appears completely buttoned.
When Frankie shows Angel her room, he puts his cigar in a wall mounted ash tray. When he leaves a few minutes later the cigar is missing as he goes.
In the major fight, Frankie Canon is knocked face-down into fairly deep mud. Seconds later he is shown "pre-fight clean" and then somewhat muddied shortly thereafter (but, even then, not as muddy as he should be).
When Sam is getting on the ferry taking him to the boat to Seattle, he finds Billy on the ferry also. Sam puts his bag on top of a crate and throws Billy overboard. When he turns to yell to George, the bag is no longer on top of the crate behind him.
In the scene when Sam McCord (John Wayne) and George Pratt (Stewart Granger) are coming out of the Palace escorting Peter Boggs to the Land Commissioner, Frankie pulls up in a wagon to race into the Palace to get Peter Boggs. When the fight starts and Frankie hits John Wayne, Wayne stumbles back. As he stumbles, he loses his cowboy hat. When his hat comes off, so does his toupee.
As he turns around and you can see the bald spots on the top and back of his head.
When Angel slaps Frankie in the hotel room, there is a loud slap when her hand makes contact with his face, but she's wearing gloves at the time. There would be no slapping sound from a gloved hand slapping someone's face.
In the cabin scene, when Billy is crooning to Angel, the scene changes from Billi to Angel in the bath. At this moment, Angel's left nipple is visible.
When Arnie swings down to help Sam under the sluice boxes during the shoot-out, the actor grabs onto the lens shade of the camera and pulls it down into the frame. The shade is visible for two to three frames.
When Dugan strikes Arnie over the head with the rifle, you can see the rifle bend. The rifle is obviously a movie prop made out of rubber.
The pole climb is purportedly shown in real time. While Sam's winning time is announced as 58 seconds, it only took 44 seconds of screen time.
Edison Blue Amberol cylinder records are played in the stateroom scene and honeymoon cabin. The film is set in 1900, but these records were not manufactured until 1912.
During the sequence when Sam and George are helping to defend the claim, you can see Mt. Whitney in the background which is in California.
The Bonanza Gold was found in Canada near the Yukon, no where near Nome Alaska.
Time line mistake: When Sam goes to help George and Arnie it takes him all night to get there (after the night cabin scene with Michelle and Billy). But after the fight at Arnie's Sam returns to the cabin the same morning (Michelle and Billy are still sleeping).