When Dr. Fiorello and Maria help Tina after her first encounter with the Faceless Man, she has fainted. Her eyes are closed, except for one closeup, in which they are wide open.
When the two doctors and Maria go in to inspect the faceless man, Dr. Carlo uses a flashlight to scan the room. In the next scene they are all fully lit and the same room is fully lit as well with multiple light sources.
The archaeologists are obviously untrained in handling dig sites or artifacts.
The "Stone Man" is actually a "Plaster Man"...the character concept drew inspiration from the famous "petrified bodies" of Pompeii. In truth, no actual bodies were excavated there(aside from some skeletal remains)...the extant "bodies" on museum display are actually plaster-cast statues created by filling hollows within the volcanic debris where victims perished, became buried, and decomposed.
At 47 minutes Dr. Mallon incorrectly pronounces the chemical phenylamine. The ending is pronounced to rhyme with "mean" not "mine". He correctly identifies it as an organic base derived from ammonia, but the rest is wrong. It is formed by substituting one of the hydrogen atoms on ammonia with a phenyl group, that is NH3 becomes C6H5NH2 (where the numbers are subscripts). He says it is formed by substituting the atoms of phenyl with equal parts of hydrogen. This chemical is more commonly known as aniline.
The dead night-watchman blinks.
In the windscreen as Maria arrives and leaves the car.
When the Faceless Man carries the female lead, who has fainted in terror, through a doorway, she raises her head slightly to avoid banging it against the doorframe.
Paul states that Mount Vesuvious erupted "2000 years ago today" when he realizes it's August 24th. This contradicts dates established earlier in the film. Mount Vesuvius is correctly stated by the narrator as having erupted in the year 79. The narrator further establishes that the story begins on June 3rd of "this year", presumably 1958.