The same furniture appears in the different houses throughout the film.
Jane/Jeanne's bedroom is on the ground floor when the vampires enter through the front door but on the first upper floor when they later try to get in through the window. When Philippe finds the room empty, it's on the ground floor again.
in episode 8 Mazamette is barely able to lift the hatbox with the artillery shell. When Satanas' assistant loads it into the cannon later, his handling shows that it actually weighs very little.
In the 2012 Kino Lorber remastered DVD, the English subtitles have some errors. In episode 8, "The Lord of Thunder", Satanas intends to rescue Irma Vep from a prison ship bound for Algeria. Disguised as a priest, he passes her a coded message which rearranges into "Le navire sautera". Colloquially, this means,"The ship will blow up", but the subtitle translates this as "Jump overboard"; probably a good piece of advice anyway, as he does arrange to explode the ship.
Later on in the same episode, Satanas plants a bomb in Guérande's apartment, and tells the paralyzed reporter that "the house will jump in five minutes"; same mistranslation.
Throughout various episodes, the same flats were clearly reused for interiors. Many of the same buildings will have the exact same wall paper and wainscoting.
In episode 7,"Satanas", Moréno several times refers to the watch on his right wrist. In close-up, the watch is on someone's left wrist.
In episode 6 the hotel corridor and the rooms don't match. The window in room 1 is in the wall where room 2 should be located, room 2 stretches so far to the right that it would encompass room 3 and room 3 has a door to a side chamber that would lead to room 2 instead.
In episode 8, when it is announced that the champagne is poisoned, Phillipe can be seen drinking the champagne well after the warning.