When the mayor makes his speech in church, there are children sitting in the pews with the adults. Then the children disappear, but they're back in the next shot.
When Ramirez sells her store, her clock is at about 11:20, then in a later scene Kane comes to see her and the clock is at nearly 11:15.
When Kane is in his office and puts his head down on his desk,
he did not have a badge on when his head went down, but he has a badge when his head comes up.
Amy's luggage has been loaded onto the train, which we see pull off without any unloading, but it reappears on the cart in the final scene.
When Kane enters Ramirez's hotel room, he drops his hat on a chair to his left. Next shot, he holds his hat in his left hand.
When Will and Amy start leaving in the beginning, they appear to travel a substantial distance away from the town, but when they get back, the clock shows only ten minutes have passed. This would be virtually impossible for a horse-and-buggy ride.
At about the 17:22 point on the DVD, the 37-star US flag is clearly seen. It has five rows of stars arranged in diagonal columns. There were three official versions of the 37-star flag and this flag does not match any of them. The official design with three rows of seven stars and two rows of eight stars has the stars lined up in seven horizontal columns with the column closet to the staff with only two stars.
Due to weather problems, the climactic crane shot at "high noon" was actually taken at 3:00 pm, so the shadows are wrong for a a "high-noon" shot.
At time stamp 34:41, Ben Miller opens the saloon doors with a bang. A man at the end of the bar trots toward Miller in the doorway slightly ducking down to avoid hitting his head on the hanging chandelier. As Miller walks back to the bar with his friend he walks into the chandelier nearly knocking his hat off his head. The actor Sheb Wooley gracefully plays this off as if nothing happened.
At time stamp 13:07, As Deputy Marshall Pell turns from the window, a small gap can be seen at the top of his shirt at the shoulder where the threads have pulled apart.
In a number of scenes there are Pabst Brewing signs seen on the inside and outside walls of the saloon. Although Pabst did brew in 1848, it did so under the name Best and Company and did not change to Pabst until 1889; the 37-star flag suggests the setting dates are between 1867-77.
The pre-gummed rectangular envelope that Kane puts his folded Last Will and Testament into was not the type used in the 1867-77 era that the 37-starred US flag suggests and was not made until about the 1890s. Envelopes in that era were diamond-shaped with the user having to provide the sealant (wax, for example).
In the climactic crane shot at time stamp 1:14:19, when Kane is alone in the town square, modern-day buildings, high-voltage power lines, and telephone poles are clearly visible in the skyline.
Although the 37-star flag suggests the setting date is within the 1867-77 frame, the date on the large boarding house at the end of the street as Amy and Helen are taking the buckboard out of town is "1888."
When Will and Ann return to town in the wagon, you can clearly see a telephone pole with three crossbeams between the branches of a tree just right of the center of the shot.
When Mrs. Ramirez's man goes to the church to fetch the man about "the store," none of the mouth movements of the actors playing choir members match the choir music (or even each other).
Early on Helen Ramirez announces she is leaving town on the noon train because she is worried about the Miller gang. However, her hotel room door gets knocked on three separate times and she simply says "Come In" She didn't seem too worried if she let people just walk into her room.