Revealing mistake: When Mulder and Scully are talking to Theresa at the diner she suddenly gets a nosebleed. If you look closely at her forehead/nose you can see the flesh coloured tube that pumps the blood. (00:33:20)
Other mistake: When Agent Comer is trying to steal the truck, he wants to hot-wire it. To do so, he unplugs the power and ignition wires in order to short-circuit them. When the owner unexpectedly appears, Agent Comer beats him up, steals the ignition key and starts the car with the key. The problem is that after unplugging the wires he cannot start the car with the key anymore. (00:20:40)
Character mistake: When Josepho meets Agent Scully, he recites to her the passage from the Bible that begins with the phrase: "Behold, a whirlwind came out of the north" Then he asks her if she knew that fragment from the Bible. She answers: "Ephesians." Unfortunately, she is wrong, because this fragment comes from Ezekiel 1:4. (00:30:30)
Other mistake: While Cadet Hayes is being interrogated, he says, "I studied the photos of your son's death. They called to me. I don't know why, but it was a message and I listened." Then Scully answers, "And then you killed Agent Doggett's son." This answer is illogical and complete nonsense because the photos of Agent Doggett's son were taken after his death. (00:36:05)
Factual error: Dogget says that "It would require something 4,300 times the density of steel to cause this damage." Steel is about 8 times denser than human flesh, so bearing in mind that density is proportional to mass at constant volume, it means that Ray would be 4,300 x 8 = 34,400 times heavier than if he were a regular human being. Assuming that he normally weighed about 80 kg, after the transformation he would weigh 80 kg x 34,400 = 2,752 tons. It means that hardly any ground would support his incredibly huge mass, let alone items such as a bed, chair, stairs, building structures, etc.
Audio problem: Fellig is confronted by the murderer and you can hear the sound of a switchblade knife opening. When the knife is shown in Fellig's back and later in the evidence bag, however, it is a butterfly knife and not a switchblade.
Factual error: When Mulder gives Scully the birthday card, she says that he is two months early. Given that Scully's birthday is on 23 February, the time of the episode should be sometime near Christmas. However, through the whole episode, there is no sign of Christmas time (not a single Christmas tree, no Christmas decorations, etc). (00:19:35)
Via Negativa - S8-E7
Revealing mistake: When Doggett examines in the car the body of Agent James Leeds, the carotid artery of the victim is pulsating. (00:05:40)
Continuity mistake: When Scully walks into Mulder's office, she stops in the position with the "I want to believe" poster in the background, then she takes a couple of steps to make acquaintance with Mulder, and she finds herself again in the position with the poster in the background. (00:05:15)
Continuity mistake: In the right shot Mulder picks the dirt with his fingers to the plastic bag, while in the left shot he pours it into the bag from the palm of his hand. (00:06:15)
Other mistake: After AD Skinner is finished being interviewed by the police, Mulder asks him about why he would employ the services of a prostitute. Skinner looks at him in shock and Mulder says "You didn't know she was a prostitute did you?" I find it hard to believe that at no point in the interview did the police not mention to Skinner the dead woman he woke up next to, after spending the night with her, was a prostitute.
Visible crew/equipment: As Scully rolls down the stairs with the killer at The End of the episode, once they reach the bottom a hand pops out from the left side of the screen.
Continuity mistake: As Lindquist holds the bag of evidence, it is hanging down in the fingers of his right hand. The next shot shows him holding the evidence bag in the palm of his right hand.
Audio problem: The first scene following the intro, when Mulder and Scully step out of the car, Scully says, "I still don't get it" but her mouth doesn't move. (00:02:30)
Continuity mistake: This is probably one of the most intriguing chess plays in the history of mankind. In the first move shown on the screen Gibson moves a white knight from e4 to f6. Then, in the close-up, the situation on the chessboard more or less corresponds to the arrangement of the figures previously shown on the screen. However, in the next shot, when we see the chessboard from the Russian perspective, the arrangement is completely different. Especially, there is no white knight on the chessboard at all. In the following shot the white rook suddenly appears on g8 (and is subsequently beaten by the black king), but in the next move Gibson again moves his white rook on g8, while the black king has miraculously returned to h8 and again beats the white rook. Moreover, Gibson could not play two white rooks, because later on we see that there is still at least one white rook on the chessboard.
Continuity mistake: During the handbrake turn Scully smiles, although in the preceding and following shot her face is very serious. (00:31:15)
The Sixth Extinction (2) - S7-E1
Continuity mistake: Mulder writes Kritschgau's name on the ulnar side of the palm of Skinner's right hand. Later when Skinner is looking for Kritschgau in his apartment building, the writing is on a different part of Skinner's palm, beginning around the middle and extending diagonally towards the thumb. (00:11:50 - 00:15:30)
The Sixth Extinction (2) - S7-E1
Character mistake: When Kritschgau is testing Mulder's remote viewing capabilities, he tells Mulder that he is at about 5% accuracy. However, Mulder got at least two right and not enough time had passed for him to have had 40 opportunities, so his percentage of accuracy should be higher than five. (00:27:00 - 00:27:45)
