Visible crew/equipment: In the scene where Lana Winters imagines receiving an award for her expose while in line for her medication, her mic pack is visible as she steps up to accept it. It is not visible in the high angle long shot before she gives her speech.
Factual error: During the Bette and Dot surgery dream, we see the bone saw machine brought in and it says "Easymatic 300." In actuality, the machine is the power source for an X-Ray machine and wasn't produced until the early 1980s, while the season takes place in the early 1950s.
Character mistake: At the table when Laveau admits she was the one who hired Hank as a witch hunter, Fiona tells Cordelia "You're not just blind, you're wilfully blind" and backhands her on the right side of her face, knocking her to the floor. On the floor, Cordelia is holding the left side of her face.
Deliberate mistake: After Elsa kicks Bette and Dot off the stage, Elsa looks at the sheet of music on the stand and you see the name of the song 'Criminal' and it also states it's by Fiona Apple which is true, but this season is set in 1952, and Criminal wasn't released until 1996.