When the film is borrowed from a neighboring theater, we see that the projector is apparently located in the balcony of the theater, not in an enclosed projection room. Furthermore, the projector has a "magnetic penthouse" sound pickup, an attachment used to play early stereophonic prints. This process would not be invented until 1953 and not used widely until years after nitrate film was phased out.
When Toto is young, the films that Alfredo gave him catch fire. They burn and ruin the only picture that his mother had of his father. When Toto is a grown up, this "burnt" picture is hanged on the wall totally unharmed.
Toto as a child is shown to be left-handed during the school examination sequence, but as a young man he is right-handed as he marks off the days on the calendar. In addition, when in the army, he fires the rifle right-handed.
When Toto is a kid, and he and Alfredo are writing the exam, Toto throws a ball of paper to Alfredo. In one frame, he is throwing it with his left hand and in another frame he is throwing with his right hand.
The heights of Toto and his mother change dramatically during the course of their adult lives. Jacques Perrin is much taller than Marco Leonardi and Pupella Maggio is much shorter than Antonella Attili. As a child and teenager, Toto is clearly below average height. In middle age, he is the tallest man at Alfredo's funeral by a clear head.
Before the theater is demolished, we see barricades in the parking lot. The camera pulls back to show the crowd watching even further back from a safe distance. Once the explosives go off, two firemen suddenly appear standing just behind the barricades.
The projection room of the Cinema Paradiso seems to have only a single projector. In those times theaters had at least two projectors and the film was mounted on multiple reels. It was the projectionists job to switch projectors seamlessly.