A scene near the end of the movie has Charlton Heston's character, Robert Thorn, talking, via intercom, to Edward G. Robinson's character, Sol Roth, as Sol is laying in the suicide chamber. At one point, the intercom malfunctions and a close-up of a light saying something along the lines of "Communication Permitted" starts flashing. For the first flash or two, nothing is wrong with the scene. But, as the last few flashes happen, look at the cable in the lower left of the screen. It starts jumping from place to place each time the sign lights and un-lights.