The fleet in the invasion of Normandy appears to consist of two ships and a pair of landing boats. The real fleet consisted of nearly 7,000 vessels, and with that number compacted onto a beachhead 50 miles in length, the ships would have almost seemed to blot out the horizon.
One of the American privates of the 29th Infantry Division landed on the beach wearing a helmet with the helmet insignia of the 327th Glider Infantry Regiment of the 101st Airborne Division (the "clubs" card suit). He could have possibly picked up a lost helmet of an Airborne trooper a few days after D-Day, but he never would have come ashore with one.
The soldier wearing the helmet from the 327th GIR called his sergeant "Sir". Sergeants are NCOs and as such, are referred to by their rank. Only superior commissioned officers and civilians are called "Sir" by soldiers.
The 29th Infantry Division sergeant that leads the invasion force tells the private that just called him "Sir" that "We gotta get off this beach, our Airborne is taking a hell of a pounding!" A few minutes later, the same sergeant says that the Airborne has been scattered all over Normandy.
Having just landed on the beach, he would have had no idea what the status of the Airborne was for at least a few days, because the Airborne was dropped inland, where their objectives were. Furthermore, it would not have been that sergeant's mission to rescue any Airborne troops. He would have had his own specific mission to worry about.
Klaus was intimidated and later arrested by a Gestapo officer. The Gestapo was a civilian police force and had no authority over members of the military.
Many of the German Mauser rifles shown in the film lack cleaning rods and sight hoods, indicating that they are likely weapons that were captured and stripped by the Soviets following WWII. German service rifles would include these features.
Many troops on both sides appear to be middle-aged and overweight. While this is common in the reenactment community, such troops would not likely have seen combat in during the opening days of the Normandy invasion.
Klaus and his fellow soldiers sport immaculately maintained uniforms and hairstyles despite being in heavy combat for long periods of time.
All of the German women have perfectly maintained makeup and lipstick, which were extremely difficult to get during wartime and were rarely allowed by regulations.
The American aircraft shown during the tank battle in Normandy is a T-6 Texan, a training plane that would never be seen in combat.
Nearly all of the German nurses are seen sporting hairstyles from the 2010s.
Weapons are often heard with generic, stock-sound gunshots. The report of the shots is often wildly different from the muzzle flashes seen.
Many soldiers are seen lackadaisically shooting and running about during combat, and very rarely seeking cover. Real soldiers would be moving much more urgently and with purpose, and would more often be in cover than not, as their lives did indeed depend on it.
The female lead, Claudia Crawford, who portrayed Klaudia Schiller, is not in the cast credit list at the end of the film. (I checked it thrice)