Not only are the black SS uniforms incorrect, as they were never worn in the field and were replaced by the army field-gray in 1939, but the SS men wear them with black ties on brown shirts. The brown shirt, which symbolized the SS as part of the SA, was discarded in 1934 after the Night of the Long Knives and replaced with a white shirt with the black uniform.
When Dr Cuza is translating the writing on the wall, he says "The form is the imperative" i.e. that it's a command. That's taken from the source novel, where the writing is translated as "Strangers, leave my home!" But in the film the translation is "I will be free", which is not an imperative statement.
The goof items below may give away important plot points.
After the two soldiers are killed releasing Molasar, a group of soldiers burst into the room. The first solider that fires into the air appears to be wearing an SS uniform and carrying a sub-machine gun. The soldiers that first arrive at the keep are Wermacht soldiers - the SS do not arrive until later in the film.
After the two soldiers are killed releasing Molasar, a group of soldiers burst into the room. To the right of the soldier that starts firing is an SS armored car. This appears to be the same car Major Kaempffer drives into the keep later in the film. The car should not be there as the SS have not arrived yet.