The first time we see Lulu, she leans on the back of a chair, a newspaper in her hand, and her right shoulder strap has fallen down. In the next shot her left shoulder strap is down instead.
While Elmer is briefing the staff before the Zenith rally, he refers to an opening "tonight". In the next scene (presumably, on the same day or later), Jim asks Sharon if she is nervous about "opening *tomorrow* night."
The first time Gantry is in Lulu's room and she is staging the blackmail photos, she puts the money he hands her into the top of the stocking on her right leg while he stands on her right side next to her right leg. When we are later shown the photograph as published in the newspaper, Gantry is still standing on her right side next to her right leg, but Lulu is inserting the money into the top of the stocking on her left leg rather than her right leg.
Approximately two-thirds through the movie, when reporter Jim Lefferts shows Gantry a newspaper headline, Gantry is initially wearing a bow-tie (clearly a clip-on - another goof for 1927), then all-of-a-sudden is wearing a necktie.
Sharon gets into the car, behind the wheel and tells Elmer to get in, which he does, on the passenger side. In the next shot, the car goes by with Elmer driving.
The movie is supposed to take place in 1927. When Lulu is waiting for Elmer, she switches on a small electric bakelite radio on the dresser. In 1927 there were no electric radios, only large wood battery operated radios. The small radio she switches on is from around 1938-1940.
Set in 1927, when Elmer is on railway tracks after jumping from a moving train, a 1950s Ford can be seen in the distance.
Sister Sharon is seen briefly outside a movie theater advertising a film. The title is not given but the stars names are given as Rudolph Valentino and Agnes Ayres, suggesting that the film is almost certainly _The Sheik (1921)_. But then in the scene with the newspapers in Sister Sharon's office, the headline on one is about death of Isadora Duncan, suggesting it was sometime shortly after Sept. 14, 1927 (date of her death). Since Zenith, Neb., wasn't exactly in the mainstream, it seems more logical that the movie house was playing an old movie since the first talkie, _The Jazz Singer (1927)_, wasn't released until a month later. So, the time line would place it in 1927, the year the book first was published.
The voice-over of the Battle Hymn of the Republic does not match the video during the Revival.
When Sharon enters Lulu's hotel room, the trip wire that is going to pull the liquor bottles off the mantle to scare the cat can be seen.
The location where Sister Sharon confronts the police captain and fire chief over erecting her tent is purported to be in Lincoln Nebraska. The opening part of the scene shows mountains in the background. There are no mountains around Lincoln.
At the newspaper office meeting, Elmer Gantry refers to Christ's miracle of feeding the 5,000 with five fishes and two loaves of bread. According to the Gospels, it was five loaves and two fishes.