Revealing mistake: When Tee Hee and Bond are fighting in the train compartment, watch the right edge of the screen. In one of the shots the end of the set is visible as Bond shoves Tee Hee against the "wall", which wobbles. So much is revealed you can see the wooden framing.
Revealing mistake: As "Tee Hee" (the man with the claw) escorts Bond to the alligator pond at the farm, they at one point stand next to each other. You can see that Tee Hee's prosthetic arm is much longer than his real one- about as long as you might expect it to be, if the actor is really holding a prop with his actual (and perfectly good) hand.
Revealing mistake: When Madeline Smith (The Italian agent credited as Beautiful Girl) emerges from the wardrobe / closet, she embraces Roger Moore. He then uses his magnetic Rolex to pull down the zipper on the back of her dress. If you look closely, you can see the cable/wire under dress pulling the zipper down. (00:11:20 - 00:12:00)
Revealing mistake: When Bond is giving Mrs Bell her flying lesson at the airport, the wings are torn off the plane. When Bond says, "Same time tomorrow, Mrs Bell?" the reaction shot of Mrs Bell shows the left wing to be intact. It is her same reaction shot when Bond climbed into the plane.
Revealing mistake: When Rosie pokes a gun through the door at the Bond's bungalow, Bond uses his cigar to burn her hand, and then throws her onto the bed. You can see that the person being thrown is not Gloria Hendry, but a male stunt double.
Revealing mistake: When Hamilton is watching the Fillet of Soul restaurant at the beginning of the movie, he is stabbed and killed. When the coffin is brought over to him, you can see the 'dead' Hamilton breathing.