Factual error: When Dorothy runs away from the hospital she is chased by a nurse, who has a torch. Earlier in this film the doctor said they two months away from the 20th century which gives the year as 1899. Such a modern torch that the nurse had was not invented yet.
Factual error: When the evangelist first enters the mansion, Mrs. Peacock calls him a beatnik. However, the movie is set in 1954, and the word "beatnik" was not coined until 1958. (01:15:25)
Factual error: When Mouth flattens the tires on Brand's bike, all he does to let the air out is take the valve caps off. There's actually a valve in the valve stem that needs to be depressed to let the air out. The cap is just there to keep dirt out of the valve, simply taking it off wouldn't let the air out.
Factual error: In the culminating scene where Fletch is held at gun point and escapes by turning on the gas valve in the fireplace and then igniting the vapors into a ball of flame, he actually turns the valve into the off position (valve is perpendicular to the pipe). (01:32:00)
Suggested correction: The valve was in closed position (perpendicular). He opened the valve (turned parallel to pipe).
Factual error: The story takes place during spring of 1976 but Marty's parents drive a 1979 station wagon.
Factual error: When Vic is in the police car, there should be a screen separating the front from back seats. (00:20:35)
Factual error: The KGB agent hunting Jonathan is carrying a Spanish Campo-Giro pistol. There's no way a KGB agent would carry a foreign sidearm in a Soviet Bloc country, especially one that was phased out of service in the late 1920's.
Factual error: During the baseball game in the beginning if you look in the background you can see several palm trees in the background. The movie takes place in Ohio where there are no palm trees. (00:09:15 - 00:10:05)
Suggested correction: Ohio is never specified as the state where the Nightmare movies take place until later in the series. As long as the state is unspecified as it is in Nightmare 2 and 1, visible palm trees are not a mistake.
All the films are supposed to take place in the same city. So if part 6 takes place in Springwood, Ohio, than so does this one.
While it would be true that the location in all previous films are now Ohio, it's hard to say if it's a mistake for the first 5 films, especially if there's no evidence for it being set in Ohio and evidence points to California. It would be more appropriate to make an entry in the 6th film saying the Ohio location contradicts what has been already seen. Otherwise, you would have to make a mistake entry every time the first 5 films reveal it's not set in Ohio, but filmed in California.
Suggested correction: Per the screenplays, the first two movies take place in Los Angeles.
I believe it was Wes Craven's intention to mention it's set in Los Angeles, but the actual script and film never state where Elm Street is located. It was an un-named suburb.