The film was shot in Germany, obviously in autumn, there are no leaves on the trees. The inserts, establishing that the story takes place in San Francisco, reveal that they were taken in summer, with green trees all around.
In the opening scene there is an impossibly convenient rope outside the window. It is too heavy to be thrown by mister Cotton to where it is and also impossible to retrieve from the other side if it's not already attached to something on the other side of the yard. Also Jerry somehow knows that the perpetrator is still in the room although from the camera's point of view we cannot see what's happening inside. And he also does not appear to have a radio of any kind to communicate with rest of the crew on site.
Camera reflected in a gangster's car in front of Ria Payne's flat.
The story mainly takes place in San Francisco, but through the window of a FBI office you can see the letters "KLEIDUNG" on a building in the background, which reveals the German origin of the shots.
The plot relies on Harry to be able to acquire blank bullets without any other henchmen noticing it and replacing the bullets that are already loaded in the magazine with them. Since he is being tailed by some goon and possibly held at the "doctor's" office this is a risky plot. And it almost failed immediately when another goon tried to shoot Cotton when they entered the quarry.
Standard police investigation practices and procedures seem to be ignored on several occasions. Important venues like the warehouse are not cordoned off and searched thoroughly. One of the weapons with silencer is left lying in broad daylight beside the cab but there is no hint of anyone recovering it nor anyone trying to trace its origins.
It is dubious that the FBI would let someone who has already been targeted by murderers to take shelter in an unknown person's apartment without any other safety measures. The FBI also seem strangely understaffed in general and don't seem to cooperate with any other authorities much.