When Sister Kathleen is in church talking to the other Sister, Kathleen's hair is in front of her shoulder in one shot and behind her shoulder in the next shot.
When Sister Kathleen is eating soup in her bed, the spoon is on her left while she says her prayers. In the next shot a moment later, she is eating the soup with her right hand.
When Chuck comes home in the middle of dinner, Nora is holding the cutlery over her plate in a side shot. In the next shot, her arms are resting on the back of her chair and then she picks up her fork and eats.
One of the young girls says that she came to the convent to be like "Sr. Gabrielle" in The Nun's Story. The character's name was Gabrielle van de Maal, but her name as a nun was Sr. Luke.
Toward the end of the movie, as a nun undresses, she is completely nude under her habit. It would have been rare that any nun would not have on some sort of undergarments in the 1960's.
At the beginning of the movie, a train is seen that consists of double stack container cars. The movie is set in the early 1960's but double stack containers were not introduced until 1984.
The nun in charge of the new girls explains that the mass will begin when the priest arrives. She further explains that the priest will have his back to the nuns and say the mass in Latin, so it can be hard to keep up. At that time, no Catholic would need to be told that the priest would have his back to the congregation or that the mass would be in Latin.
During the clothing ceremony, Nora is in church without a hat or veil. She would have been required to wear one in church.