Where Brigitte goes to the German HQ, the two guards at the entrance wear the correct uniforms, but their boots are the kind used by US forces.
When Ensign Kim reports to the Hirogen that there has been a simulated explosion on Holodeck 1, he states that it blew out the holo-grid across THREE decks; however, just a few seconds later, the scene cuts to the Holodeck where we can clearly see FOUR levels of Voyager's interior exposed within the program. Three levels of deck plates would separate four levels of the ship, so Kim's statement is accurate. The deck plates of the lowest exposed level and the ceiling of the highest exposed level are intact.
Inconsistencies with character appearances. Other than changes in dress, most of the time all characters maintain their normal appearances; e.g. Tuvok's ears, B'Elanna's forehead. However, in the opening scene, Janeway is made to look like a Klingon.
Not only was the Citroen 2CV not produced until after the war, but the red and black model shown was a 'Charleston' which was not sold until 1980. A number of the pre-production TPV (Tout Petite Vehicle) were produced before the war but these were hidden or destroyed when Germany invaded.
When Brigitte travels to the Nazi base in 1944, a 1949 Citroen 2CV car passes by.
At the beginning of the episode, Janeway fighting in the Klingon simulation, and is made to look like a Klingon, but when Seven, Torres, Tuvok and Neelix are in the WWII simulation they look like their normal characters, and when Neelix is put into the Klingon simulation (seen in Part II) he is not made to look like a Klingon.
When Neelix comes back from his first delivery, he says that he has befriended most of the men of the Gestapo. That is not possible in France because the Gestapo was rarely active outside of Germany and Austria.
Furthermore Gestapo men would not be on garrison duty.
The doctor says he can barely keep up with the extensive physical damages to the crew by the Hirogen, yet only two patients are ever seen, and the Doctor's movements are not urgent.
When the Hirogen discover the Doctor has disabled Janeway's neural interface, one of them holds the Doctor in a lock and at phaser point - somewhat useless as he's a hologram and a phaser could not harm him.
Tuvok says that the Hirogen Kommandant, who wears a Schutz-Staffel Uniform, served under Generals Erwin Rommel in Afrika and Rudolf Schmidt in Poland, but the SS were never active in those regions, so the Hirogen should have worn a normal Wehrmacht uniform.
The Hirogen second-in-command wears a lieutenant's insignia but gives orders to the Schutz-Staffel Garrison 2nd-in-command, who is, supposedly, a captain (a higher rank).