Revealing mistake: When Max Zorin first tries to attack Bond with a fire-axe in the duel on Golden Gate Bridge towards the end of the movie, you can see it is not Christopher Walken but his stunt double. (01:59:20)
Revealing mistake: When Bond and Tibbitt are in the underground lab the big henchman takes out Tibbitt. When the henchman turns to take out Bond you can see Tibbitt in the background unconscious. It is not Patrick Macnee but a stunt double. (00:38:30)
Revealing mistake: When we see James Bond climbing up the cable on the Golden Gate Bridge, you can see that it is not Roger Moore but his stunt double. (01:57:30)
Revealing mistake: When Bond is being chased down the mountain by the chopper, at one point the camera does a close up. As it does, Bond appears to have a dark line around him, and the background is blurry. This is because he's on a sound stage, and the rest is projected behind him. (00:03:00)
Revealing mistake: When Zorin shoots Mr Howe dead in his office at San Francisco City Hall, you can see that Mr Howe has a bullet effect pack visible under his shirt. (01:23:40)
Revealing mistake: When Bond and Ivanova are at the Japanese spa, steam is coming from somewhere in front of the water, not from the water itself. (01:05:10)
Chosen answer: Zorin is a psychopath. He may have meant it when he told May Day he loved her, or he may have just been telling her what she wanted to hear. Either way, when he thinks she'll drown in the mine as well, he doesn't consider it worth scrapping the plan just to save her. Once she escapes and has the bomb, he looks shocked partially because she wasn't killed but mostly because she's chosen to sacrifice herself to thwart his plans, something that a self-interested psychotic personality can't comprehend.
Captain Defenestrator