In the French restaurant, Patricia's hand holding her cigarette jumps from her face to the table and back between shots.
The film is set in New York City (established with the liberal use of stock footage) but filmed in Spain, with all dialog dubbed after the fact. Thus there is a scene in the middle of the movie where Paul and Patricia walk out of a candy store onto the sidewalk, go past a sign on a lamppost declaring it to be the corner of E 57th St, walk down a staircase into what should be the street (there are no staircases along the length of Manhattan sidewalks, and they are all a single step above the street), come around the corner into a pedestrian walkway with a fountain instead of a street (but which also has a sign declaring it to be E. 57th St, meaning they're at the corner of E. 57th St and E 57th St), and walk past a tree which briefly obscures the camera shot. As the dubbed dialog continues the conversation without missing a beat, the camera cuts from the tree to a shot of them walking down a completely different street that looks absolutely nothing like New York City. They are now walking past a blue building, with no sign of the tree or the bright red building from the previous shot. Behind them is another sign declaring that this is also E. 57th St, although the shape of the sign is different and the sign is in the middle of a pedestrian walkway. At no point during their conversation is there a street or a car in sight. A few seconds later, the movie cuts to stock footage of the Brooklyn Bridge, which is several miles from E. 57th St.
When the robot kidnaps Prof. Morgan, Gulik watches through the only camera in the room - the one in the robot's forehead. And yet, the image displayed on his monitor shows a view of the robot from several feet away shot from waist height.
American soldiers use British Sten guns.
The "steamroller" Supersonic Man lifts up during the car chase is VERY obviously a cheaply-made wooden prop.
The TV news on-location interview with the research center's chief of security is shot like a feature film, not a television news broadcast.
Some shots of Supersonic Man flying through the city does not always correspond to the footage shown. In one case, he appears to be flying straight, while the background image of the city shows the shot panning.
A car spontaneously explodes while driving down a slight grassy incline.
The car chase suddenly moves from somewhere in Manhattan to a semi-rural suburban area hours away from Manhattan in ordinary traffic.