Factual error: Hannibal makes a bomb using latex gloves that were not in use during the early 50's when the movie takes place.
Continuity mistake: Hannibal incinerates Zigmas Milko's dead body with his (Milko's) dog tag in his (Milko's) mouth. When Hannibal confronts Grutas while he (Grutas) is bathing, Hannibal tosses a dog tag at him, which should be Grutas' own. Soon after however, the camera shows the very same dog tag that was supposed to have been incinerated with Milko: "Zigmas Milko 03402810 3/ INFRGT33".
Factual error: In the scene where a young Hannibal dissects the corpses in the mortuary, there is a black and white coronal MRI slice cutting through eye-balls and fronal lobes of the brain on the wall. MRI was invented in the 70s.
Other mistake: In the final scene, as Hannibal drives away, the car is spotlessly clean - after driving hours on slushy roads, the car should be filthy.
Continuity mistake: When Hannibal is at the writing desk, he sits with a pencil in his left hand. A banker comes in to the chateau to speak with his aunt, and the camera shows Hannibal listening in to the conversation. While this is happening, he puts the pencil down. There is a quick cut to a different angle, and the pencil is in his hand again, with no time to pick it up, and the next shot shows him putting the pencil down again.