(at around 1h 50 mins) The page Gerstein pulled out from the printer has a different text than the page he is signing with a Himmler's sign.
At the end of the film, on the screen we read that Gerstein's written testimony helped to validate the events of the Holocaust. Then, "Kurt Gerstein was rehabilitated 20 years later." He could not have not been "rehabilitated", since he was found hanged in his cell in 1945. "Rehabilitated" should have been "exonerated".
In one of the scenes they say that the Treblinka camp is out of gas, referring to Zyklon B. Treblinka didn't use Zyklon B, instead they used carbon monoxide.
After 10.10 in the film, the car passing is an IFA F9, which was produced in Germany from 1949 to April 1956.
In addition to the black SS parade uniforms worn by characters in the film long after their discontinuation in 1939, earlier scenes show these uniforms adorned with the swastika armband of the Hitler Jugend, The Hitler Youth, not the black rimmed armband of the Allgemeine SS and other branches of The SS wearing the black tunics of the 1930s.
A porter refers to Kurt Gerstein as a "captain". Actually his SS rank is the "Obersturmführer" which is the equivalent of an Oberleutnant in the German Wehrmacht. (at around 23 mins)
As late as 1944, several of the SS officers in the film are shown to be wearing black parade SS tunics. The black SS jacket was phased out of the SS in 1939 and had been completely discontinued by 1941 in favor of the gray wartime SS tunic.
(at around 1h 25 mins) When Kurt is visiting an old friend for support, some shelves have modern folders.