Other mistake: During the scenic elevator rescue scene, a helicopter lowers the Fire Chief down to connect a cable to the top of the elevator. The cable is seen to be hanging no more than three feet from the side of the building. If this were the case, the helicopter's rotors would be hitting the building. (02:04:10 - 02:06:10)
Other mistake: When young Vito Corleone shoots Fanucci in the chest at the doorway to his apartment, in a continuous shot, a wound/blood bursts from Fanucci's white vest. When Fanucci proceeds to tear his vest open seemingly in disbelief he has been shot, there is no entry-wound, blood or hole in his white shirt directly under where the wound appeared in his vest.
Other mistake: During the quake, we see the furniture, wall panels, ceiling tile, windowpanes, vertical blinds, etc., in the office fall, shake, or crack. Yet the leaves of a large potted plant do not move at all.
Other mistake: At the start when Crewe's girlfriend says "don't you take my Maserati" Crewe says he has earned it. He then goes out and gets in a Citroen, not a Maserati. Also, a Citroen front license plate appears on the car shortly afterwards which wasn't there before. (00:03:57)
Suggested correction: The Citroen SM model has a Maserati engine.
That doesn't make it a Maserati. Citroën bought Maserati in 1968, but their badge determined the brand, not what engine was in it. A lot of car companies are owned by other car companies to have multiple divisions in their lineup. If someone has a Toyota and called it a Lexus, they'd be wrong, just like it's wrong in this case.
Other mistake: As the rescue copter is lowering down the pilot, it can be seen flying above and in front of the jet so he can enter into the hole above the copilot seat, but passengers looking out of the side windows of the plane can see the copter and that the first guy fails? Not possible.
Other mistake: In the original version of the film there's a mistake in the opening credits where Colin Blakely's name is misspelled as Colin Blankey.
Other mistake: When counting out Adam Faith in the boxing match, the referee counts 1 - 4 in Spanish then (with his back turned to camera) adds 'cinque' - Italian. I suspect this was dubbed post-production because the location of the scene was in Spain and the actor Spanish.
Other mistake: When Celine (as Julie) meets up with Guilou in the park whilst he is sitting on the bench, a man in a suit with a briefcase can be seen walking past in the background, who looks at the camera a couple of times while walking past. (00:45:50)