Revealing mistake: Bond escapes from the buried pipeline when two technicians open a hatch from the outside. One tech unlocks the hatch by rotating a large wheel which drives the locking mechanism. But when he finally opens the hatch, there's absolutely no mechanism attached. There's just a bare axle that the wheel turns on.
Revealing mistake: In the scene with the helicopter chasing them down the street, apart from the fact that the rotors should catch on something and hurl the machine into a wall, when it finally hits the wall at the end, the pilot and crew quite clearly become about 4 crash-test dummies. This wouldn't be so bad if it weren't for the fact that they are unpainted and all sit in their seats looking straight ahead with their hands in their laps while they are driven into a wall. You'd think they could have at least posed the arms over their faces or SOMETHING!
Revealing mistake: During the draining of the water in the dish, some shots show the water moving backwards. For instance, at a particular moment, masses of water jump UP, ark toward the opening, and fall in it. The most likely reason is that, during the filming, the special effects people took a shot of a replica of the dish FILLING with water, then edited it the other way, to show that the water was emptied from the dish. (01:42:00)