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.