Factual error: When the real German soldiers are playing 20 questions in the bar, one of the cards shows the name of Genghis Khan. This is an English-language word; as Germans, they would have written Dschingis Khan instead. As the whole scene deals with exposing the British/American spies and subtle differences in their language or behaviour, this is especially unfavorable here.
Factual error: In the opening scenes by the farmhouse, the fields in the distance have "tramlines" - used for accuracy when crop spraying. The scene is set in 1941 however tramlines didn't come into use until the 1950s. (00:02:20)
Factual error: During his briefing for Operation Kino, Lt. Hicox quips "Paris when it sizzles", which was not a thing in WWII; it is the title of a 1964 film, itself taken from the 1953 Cole Porter song "I Love Paris."
Factual error: During the baseball bat beating scene, the "hitter" says something about Teddy Ballgame going yard. "Going yard" is more like a 1990s term, not one used way back in 1941.
Factual error: After carving the swastika on the Nazi private's head that they let go, Donny tells Aldo that he's getting good at that. Aldo then proceeds to make the joke about getting to Carnegie Hall and practice. This has been a well known and common joke for years, however the earliest known written instance of this joke is from 1950. Plus the joke originates in New York and Aldo is from Tennessee, saying he's from the Smoky Mountains. So him referencing this joke in such a manner does not match the time frame at all and is way out of place.
Factual error: When Colonel Landa offers to surrender in exchange for not warning Hitler he is about to burned alive in the Paris cinema he points to a telephone with a rotary dial with alpha-numeric characters. I believe that was a feature of North American telephones after WWII.
Factual error: Before the Kino operation, Shosanna makes a sexy move showing her side, acting like a styled actress and says "Catherine Deneuve." Meaning that at that time Catherine Deneuve must have been some well-known French actress. The problem is that Catherine Deneuve was born in 1943, so in 1944 she was probably 1 year old.