At approximately 15:04, Scully is typing at her computer, while dictating her entry to the audience. However, the text on the screen is actually ahead of her narration, and the text we see she has typed will be entered again, moments later.
When explaining how the death occurred, it is said the servo was tampered with and that the ground was connected to the negative. Firstly, the item being pointed to on screen is certainly not a servo, at best a servo controller. Secondly, ground is the "negative" when it comes to power. Data lines may be labeled as negative. Regardless, none of these situations would cause the handle to be electrified. In fact, the hot lead, not the ground, would need to be tampered with.
(at around 41 mins) The same shot of Claude Peterson is shown twice, first normally and then in reverse to make it seem like he is looking left and right.
At 29:34 the camera pans around as Mulder and Scully turn and a man can be briefly seen walking in the background. In the very next shot, as Scully faces Mulder, the same man can be seen standing still in the middle of the path. His briefcase can be seen moving, so it's not a static image.
At 13:23 on the DVD version of the episode when Mulder and Scully are questioning Brad Wilczek, he wants to show them the computer system that runs his house. The shot of the computer monitor reveals the behind the scenes crew in the reflection just before Wilczek turns the screen on.
An elevated train is seen in some background shots in Crystal City, Virginia. Although the Washington Metropolitan Area Transit Administration has elevated subway tracks throughout the Washington, DC, area, many of which look similar to this, the train shown is actually the Vancouver SkyTrain.