Revealing mistake: When Bond horseback rides towards the plane, Roger Moore is replaced by an obvious stunt man wearing red goggles. (02:02:50)
Revealing mistake: Near the end, When Bond is hanging onto the outside of Kamal's plane (first on the roof, then on the side), we see two instances of Roger Moore's stunt double. (02:04:13 - 02:05:10)
Revealing mistake: When Gobina first slashes at Bond during the climactic fight on the plane, a subsequent medium shot reveals a stunt double (note the bald spot). He's even wearing completely different clothing - a black stunt suit instead of a blue jacket and white shirt. (02:05:00)
Revealing mistake: In the scene where Bond is trying to escape with his new Mini-Jet, he flies through a big hall. If you look carefully, you can see that the aeroplane which is supposed to be flying with its wings vertical is fastened to some kind of sustainer.
Revealing mistake: When Bond and Gobinda are fighting on top of the train, Gobinda rolls over with his sword, which bends like a rubber prop.
Revealing mistake: When the police cars chase Bond and stop outside the circus, you can clearly see a lot of brake-marks. It's quite obvious that the filmmakers re-shot the scene several times, before they got it right, but didn't bother to remove the marks made in earlier takes.
Revealing mistake: When the plane comes out of the horse box you can see that the undercarriage is fixed and that the wheels cannot retract like they do in the next scene. This version of the plane is the same one at the petrol station where the controls are the same as a motorbike with handlebars and a throttle, steering was done using the front wheel.
Revealing mistake: When Bond throws the baddie on the bed of steel spikes, the spikes bend revealing they're made of rubber (despite a crunch and a yell of pain being heard).
Revealing mistake: When Bond is driving on two wheels, the stuntman behind the wheel is very noticeable, mainly because of his toupee.
Revealing mistake: On top of the plane, Gobinda's stunt is noticeable because he has less of a beard.
Revealing mistake: When Grischka pins Bond to the cabin door with his knives, he takes out a knife and attempts to kill Bond for killing his twin brother. Bond then opens the cabin door and then kills Grischka by opening the cabin door and throwing a knife into his stomach. If you watch carefully, you can see the cabin door begin to open before Bond pulls the cabin handle down.
Revealing mistake: When Bond falls off the train the scenery switches from outdoor filming to an obvious film set.
Revealing mistake: When Bond exits the carriage at the tunnel, it's an obvious stunt double.
Revealing mistake: When Bond jumps out of Kamal's aeroplane with Octopussy, you can see that Bond is not Roger Moore but his stunt double.
Revealing mistake: When Bond sends an assassin crashing into the tank containing the octopus, you can see the assassin is a dummy.
Revealing mistake: During the climax when the plane explodes, you see a shot of Kamal Kahn screaming, the you see it explode. When it explodes you can see the plane is crumpled up before it even hits the ground.
Chosen answer: The satisfaction of knowing he'll win, the thrill of pulling one over on someone; maybe like Goldfinger, he just doesn't like to lose under any circumstances.
Captain Defenestrator