In every other episode, the ice pick to the nape of an alien's neck releases toxic fumes, along with the ichor, but in this episode, when Agent Spender and Krycek kill the rebel alien, they are unaffected by the exposure of the ichor to air, which should have been toxic for them to inhale.
The special effects operator and his fire rig are briefly visibly when the rebel alien kills the Syndicate elder while disguised as Dr. Openshaw.
On-screen graphic identifies as location as "Silver Springs, Maryland"
The correct name is "Silver Spring".
Cassandra Spencer is supposed to be quarantined when Scully takes her out of the hospital room, yet the FBI guard makes no attempt to stop them from leaving.