When Michelle is telling René about the cafe that was the previous safe house she says that the cafe was in Nouvion. In subsequent episodes it is established that René's cafe is in Nouvion. There may be other cafes in Nouvion but if the owner and his wife were shot in the town square René would know about it.
At 7:36, when René calls Yvette and Edith into the back room, the chair Edith puts on the table falls off and nearly hits Yvette, who nimbly moves round it and carries on with the scene. In the 1980s there was very little time (and no budget) to do retakes, with most episodes being shot "as live" so little imperfections like this were commonplace.
Lieutenant Gruber stated to René that it got lonely on the Russian Front (implying his covert homosexuality). As the German army did not invade Russia until June 1941, the episode must be set after then. However, some sources state that this episode was set in 1940.