Factual error: Mulder mentions the USS Eldridge as disappearing from Philadelphia (and later reappearing in Norfolk) "nine months after Roswell", i.e., May 1948. In fact, the supposed incident took place much earlier - in February 1943, according to almost all reliable sources.

Continuity: When Mulder and Scully are on the boat and check the other boat in the radar, you can see that the first time, the boat in the radar is at the center left. When it changes angles, the boat is now at the center right.

Factual error: The Norwegian bar has a Norwegian flag on the wall. In the '90s no Norwegian bar would have the country's flag on its wall unless it was a racist/Nazi bar.