When Frank confronts Cora with the money after returning from the bus depot, he is standing in front of a clothesline where a sheet alternates between being tightly pinned and sagging between shots.
In the ending scene, as Frank is caressing Cora's hand, Franks left foot is in between the rock and the hat, and Cora's hand is about a foot away from both. In the next shot, her hand, the rock, and the hat are right next to each other and Franks foot is gone.
A knot in the sling that Frank has on his right arm appears and disappears when he is talking to Sackett in the hospital bed.
Mr. Katz pencil moved from the left side to the right side of his pocket when he and Chambers talked in the basement of the courthouse.
In the final scene, after Cora dies and Frank sobs beside her body, you can clearly see Jessica Lange's chest move as she breathes.
Modern-day paper currency is used in craps game set during Great Depression, instead of silver certificate dollar bills then in use.
(at around 1h 35 mins) When Cora walks to the door of the café after coming back from her mother's, her zipper and zipper pull show. What we see is an "invisible" zipper which were not invented until the early 1960's.
During the party there is a 48 star US flag and the current Greek flag (blue and white cross in canton and blue and white stripes). But the setting is the Great Depression and at that time the Kingdom of Greece had a blue flag, with a white cross on it (no stripes) and a gold crown in the middle of the cross. The flag with the stripes would not be adopted by Greece until 1978.
When Frank and Cora attempt to leave for Chicago, a portion of a modern skyscraper is clearly visible at the top of the frame as they cross the street.
When the car goes down the hill the first time, the passenger door comes open and a person can be seen exiting the car through it (1:03:48).