The Fiat car used by the Mechanic in the case in
Naples area is blown up. However the car is used again a few minutes later. Not only is the registration plate the same, it still has only one brake light working.
At the end of the movie, when Steve takes the taxi to Arthur's house, you can see Steve's car and there is clearly no note attached to the rear view mirror. When Steve leaves Arthur's house and goes to his car there is a note on the rear view mirror. This should have been visible from the taxi.
After the driver of the Chicken Lickin truck gets out, the door closes. In the next shot, Steve is seen closing the same door.
When Steve pulls up to Bishop's house he pulls the car into spot facing in then in Italy Bishop is killed when Steve pulls up in taxi at Bishop's house the car is now facing out who moved it.
When Bishop pins up the papers that he gets in the special delivery, he puts the pin in the top middle of the paper. In the next shot, the papers are pinned in both the top left and right corners.
When Bishop is photographing the first victim's apartment from across the street the bed is to the far left of the window, yet when Bishop is later reviewing the pictures he took back at his home he looks at a picture of the bed and side table with a clock but from the position that the photograph had been taken it could only have been taken inside the victims room looking towards the window, a shot which would've been impossible for Bishop to take from across the street.
(at around 1 min): When Bishop is photographing using a telescope, the image
should be upside down.
Arthur Bishop, played by Charles Bronson, tries to destroy the photos of his victims in his fireplace. That would be fine in a wood burning fireplace but his is gas.
Correction to and explanation of a factual mistake. It was stated that in the opening scene the Questar telescope should produce an inverted image. That is true if an eyepiece is used, but the penta-prism in the camera viewfinder re-inverts the image to be right side up. The telescope functions as a telephoto lens and presents a normal inverted image to the film plane.
When The Man is shown painting the leopard, there is no paint on his brush.