Other mistake: In the police station, Scully looks twice at a photograph of one of the dead kneeling girls, whose eyes should be burned out in the photograph, but they are normal.
The Post-Modern Prometheus - S5-E5
Continuity mistake: Izzy unwraps a peanut butter sandwich and sets it on a bare tree stump as bait for 'the Great Mutato', then he steps away with the others. When we see the Great Mutato hurriedly put it down, a paper bag is suddenly sitting on the stump beside the bitten sandwich.
Revealing mistake: The dead Mrs. Sim is supposed to be nude in the bathtub, but for a brief second, a glimpse of her head and shoulders reveals the very top of a flesh-coloured modesty wrap covering her breasts. This may not be visible in a non-widescreen format release.
The Pine Bluff Variant - S5-E18
Other mistake: On the information text at The Beginning of the scene telling the viewers where the scene is taking place, it is written as the "First Sovereign Bank of Pennslyvania" in "Harrisburg, Pennslyvania", instead of Pennsylvania, misspelling the name of the state both times.
Factual error: When Byers asks Langly to try under active cases to find Holly Modeski in the FBI database, Langly only presses two or three keys on a keyboard, which is obviously not enough to enter "Holly Modesky" to the search engine. (00:19:40)
Factual error: When two unidentified men who approached Susanne Modeski in the warehouse take out their handguns, they have regular pistols. However, when they start to shoot, continuous fire is heard that could only be produced by an automatic weapon. (00:28:40)
Suggested correction: Fully automatic pistols exist, such as the Glock 18.
Continuity mistake: During the shootout in the warehouse, a wedding ring is visible on Mulder's finger. While it's possible Mulder was married before, the Lone Gunmen are shown hacking into Mulder's FBI dossier and Langly reads out that he is single.
Factual error: When Suzanne Modeski retreats to the restroom with a pair of pliers to pull out her tooth, she is only gone for approximately 15 seconds before the gunmen follow her. For a petite woman to rip out a strong, healthy molar from her own mouth (which also had metal prongs Underneath in her gum) would not take so little time, no matter how determined she was. It's also highly unlikely that the lack of anaesthetic would have allowed her to do so without making pained noises.