Visible crew/equipment: When Mulder and Scully enter the abandoned mine through a doorway, the viewer can see at right in the distance a number of people sitting on a wall, and one crouching in front of the wall with what looks like a dog. They are sitting still, but there is still movement there.
Continuity mistake: In the mine with the medical records we see Samantha's file. In the season 1 episode "Conduit" we see the X-File Mulder opened on her. In the previous episode she is listed as Samantha T. Mulder and her birth date is 1/22/64. Here we see her name as Samantha Ann Mulder and her birth date as 11/21/65.
Factual error: Mulder tells Scully that he is trying 27828 and it is not working. It is not surprising that it is not working, because the Napier constant is not 27828, it is 271828. Plus they somehow they know how many digits from this constant should be entered on the keyboards.