When Mulder is standing outside of Arthur Dales' apartment talking to Dales' brother there is a mistake on the newspaper Mulder is holding. The paper was supposed to of been written in 1947, however on the left-hand page an article about a college professor who went missing in October of 1995 can clearly be seen.
Mulder goes to Arthur Dale's apartment looking for Arhtur. However in the episode "Agua Mala", which aired earlier in the season, Mulder and Scully go to Florida to see Arthur. Therefore, Mulder already knew that Arthur lived in Florida so why would Mulder go to Arthur's apartment to find him?
At several points, including at the very opening when they are hit with baseballs, we see Saguaro cacti around what we are told is "Roswell, N.M.". While they are the most widely recognized of all the cacti, Saguaro cacti have a fairly small growing environment. That environment does not include the State of New Mexico.