Revealing mistake: After Mayday drops the recalcitrant businessman out of the zeppelin, there's a long shot of him falling into the water far below. An obvious dummy, his legs are flailing much too limply (and in too many directions) to be human. (00:56:10)
Revealing mistake: When Bond jumps on top of the elevator in the Eiffel Tower you can see briefly that it is not Roger Moore but his stunt double. (00:18:35)
Revealing mistake: When Zorin falls off the Golden Gate bridge, you can see in the long shot it's just a dummy. (02:00:05)
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)
Revealing mistake: During the fire truck chase in San Francisco there's a long line of people watching the filming.
Revealing mistake: When Bond climbs out of the burning elevator he is not Roger Moore but a stuntman. (01:29:14)
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