In one early scene (in the church) Inge says in German, "Ich bin eine deutsche Fräulein" ("I am a German girl"). This is completely wrong German - a glaring grammatical mistake far too basic to be explained away as part of her character. "Fräulein", like all diminutives in German, is a neutral noun, so the correct rendering should be, "Ich bin ein deutsches Fräulein".
Corn plants shown in the film were spaced only inches apart. In the 1920's each plant was spaced much further apart. Horse drawn planters used "planting chains" anchored at ends of each row so the distance between each row would equal the distance between each plant.
In several prominent scenes both on farmsteads and in the church, there is a farmer with a "Carhartt logo" on his work jacket. Although the Carhartt company made work clothes since 1889, in the 1920's they were mostly worn by railroad workers, not farmers. In addition, the "C" type logo was not used until much later.
They harvest an entire field of corn between the two of them, when they get back to the barn, the crop is suddenly wheat. They go through the whole "separating the wheat from the chaff" process, and pour the seed into sacks.
When Olav finds Inge in his house in the morning and then they go out to the barn, there is inconsistency in the time of day of the indoor and outdoor shots. In some it is gray/early morning and in others the sun in high in the sky and it is mid-day.
During the train depot scene, the pendulum of the regulator clock on the wall is not moving yet as the scenes progress, the hands of the clock move from 2:10 to 3:30. Impossible for hands to move without the pendulum as it was not an electric clock and certainly not a quartz movement circa 1920.