Factual error: When Mulder wants to shoot the third resurrected agent, it turns out that there is no ammunition left in the revolver. In fact, there should be one bullet left. When Frank Black takes the handgun from the necromancer, one can see that the cylinder is full with six bullet. Then, he fires three bullets into the first resurrected agent and two bullets are fired by Mulder into the second resurrected agent.
Factual error: When Mulder is visited by his mother, he definitely shows brain activity, because he is "talking" with her, however there are only flat lines on the monitor. In a similar situation in "The Sixth Extinction" episode, when Kritschgau and Skinner ask him questions and he anticipates them, the monitor shows intensive bursts.
Factual error: When Skinner is at Kritschgau's apartment building, the time stamp onscreen says it's 5:05 AM, but when Kritschgau answers his door, he says it's 6:00 in the morning. Plus it is shown to be broad daylight outside. The sun is never up that early in Washington, D.C.