(at around 3 mins) When the lady at Hannibal's dinner party says, "Hannibal, confess. What is this divine-looking amuse-bouche?" she has a full plate of food in front of her. An amuse-bouche is a bite-sized morsel, or hors d'oeuvre, not enough to fill a plate.
The Georgia state flag that appears in the movie was the current state flag of Georgia in 2002, but Georgia had a different flag in the 1980s - when the movie takes place.
(at around 1h 8 mins) When Will is teaching Molly to shoot at the farm, there is no visible recoil when she discharges the revolver. This would be practically impossible with a 357 or 44 in the hands of a novice. There is no flash either, just wisps of smoke. In fact, the gun shakes more while she's cycling the cylinder then when she discharges it. There are also no bullets in any of the chamber. Finally, neither are wearing safety goggles, which as a FBI field agents should be second nature when firing in a range-type setting.
Actor Ralph Fiennes speaks with an impaired speech, mentioned as due to his character's Cleft Palette repair, but when we hear "flashbacks" to his childhood through voice over, the child voice actor portraying his character's younger self speaks without impediment.
Before setting him on fire Dolarhyde, "The Tooth Fairy", forces Freddy Lounds to dictate his manifesto on a tape recorder and then delivers the tape to the FBI by putting on the wheelchair that Lounds is glued to. Dolarhyde then sets Lounds and the wheelchair on fire and sends it rolling down a street, and yet the tape somehow survives and avoids being melted by the fire.
(at around 42 mins) When Francis is doing bench presses, a camera operator wearing a black t-shirt is reflected in one of the mirrors.
(at around 1h 17 mins) When Dolarhyde speaks closely to the captive Lounds, the scar on his upper lip is falling off.
(at around 9 mins) When we are first allowed to see Dolarhyde's scrapbook, various newspaper clippings are surrounded by Dolarhyde's marginalia. On one page of a printed article, the reporter sought to describe Lecter's cannibalism, especially in reference to serving human remains to guests; in that article, the text reads that he cut "mussel" from the bone, a spelling error no respectable newspaper would allow. Later (at around 50 mins), when we see the "Red Dragon" illustration within a book, the blurb on the opposite page tells what museum is archiving it, but refers to the series as illustrations of "Revelations" (the book in the Bible has a singular title), an error a prestigious museum would not let pass.
After Dolarhyde force Lounds to read from the note, they have a brief talk. After that Dolarhyde bite Lounds face and Lounds scream. When the FBI agents hear the recording, there are no brief talk. Immediately after Lounds read the note, Dolarhyde bite his face. Does Dolarhyde edited the recording?
(at around 4 mins) The tan leather shoulder holster worn by Will Graham in the opening of the film is a Galco Miami Classic model that was not yet available in 1980 when the scene was supposed to take place.
(at around 1h 18 mins) As Lounds is rolling down the street in the wheelchair, ablaze, his arms are no longer glued to it. And because of the moving arms, you can see that it is a stuntman covered with a black material.
(at around 1h 18 mins) There is a cord visible when the burning wheelchair is rolling down the street, and is also indicated by a trail of fire left behind it when it has fallen over.
(at around 1h 40 mins) After Graham finds out the video tapes are what links the victims the aircraft flying at dusk is the outline of a Falcon 2000. The film takes place sometime in the early '80s and the Falcon 2000 was not delivered until March of 1995.
(at around 1h 35 mins) When Dolarhyde is at The Brooklyn Museum, the woman who shows him the painting has eyeglasses hanging on a chain around her neck. After she says, "It's remarkable, isn't it? Two hundred years old... looks so fresh... so vivid", as Dolarhyde leans in for a closer look, she is now wearing the eyeglasses on her face.
(at around 1h 55 mins) Dolarhyde attempts to break through the bedroom door but stops just after damaging the door jamb. Later, after the shooting, Molly has to break the slats to get to her family, but the door jamb is intact.
(at around 11 mins) At the end of the title sequence, following the prologue, the unseen killer rapidly flicks through the pages of his journal. Going through this sequence frame-by-frame reveals two identical pages - highly implausible in a scrapbook-style journal (The repeated page consists of one boxed article at the top, a picture at the bottom-left, and part of another article at the bottom right, the text selectively obliterated with a black marker pen).
The first time we see the "Tooth Fairy"'s tattoos, the rear view clearly shows him to be naked. When he turns around, however, although he is figleafed by a towel, his jockey shorts are visible.
(at around 48 mins) When Lecter acquires Graham's address, the pulses heard in the handset do not match the ones he is tapping out. When you make a call this way the number of pulses you hear are matching with the tapped ones.
(at around 1h 11 mins) When Dolarhyde cuts the bindings on the tabloid, he uses a bolster-lock stiletto with a bayonet style blade. In the next shot of the knife in his hand, when he is confronted by the newspaper seller, it's a swinguard lockback (no "picklock" or liner lock mechanism is visible at the bolster, making it a lockback) stiletto with a "standard" style blade.
(at around 1h 22 mins) When Lecter is saying, "Clever work on his note, by the way," the camera is reflected in the glass under Lecter's chin.
(at around 1h 8 mins) When Molly learns to shoot at the farm, every shot she takes echoes, but Molly and Will are in an open plain. The only way for the shot to echo is if they were in an enclosed space.
(at around 8 mins) In the beginning of the movie, immediately after Lecter stabbing Graham, the detective falls down, along with a basket full of arrows. Then he stabs Lecter with the arrows. When Lecter gets up, the camera shows Graham on the floor, but with no arrows or basket along his right side. On the next camera shot, the arrows are back in place.
When Molly shoots Dolarhyde in the cheek, he blinks. Her first shot went through his forehead, a fatal shot. His eyes could not have blinked.
(at around 44 mins) Dolarhyde is circling/marking out an image of Freddy Lounds in a clipped article in his journal. In the next shot as he's turning pages, the image is circled but not marked out.
(at around 1h 26 mins) At the point when Reba McLane is examining the sedated tiger her wristwatch watch reads 11:20 (though the hour hand is out of sync). However 30 seconds later on the same scene, the veterinary assistant's wristwatch watch reads just before 11 o'clock.