Wilhelm Grimm initially appears in the uniform of the SS and then later appears in a Wehrmacht uniform. This is unlikely. It was more likely to be the other way around towards the end of the war when SS soldiers tried to hide their SS involvement by disguising themselves as ordinary solders.
Grimm's left eye, which is his glass eye, is seen to act and move like a natural eye throughout the movie.
When Grimm is being led through the town by a policeman, a shadow of the camera and a crew member is visible falling across the following townsfolk, especially on Anna's father.