Revealing mistake: When Willie and Short escape the jet of water and Indy climbs the mountain alone, the river below is totally still (impossible because of the huge amount of water that's falling on it), revealing it's a still image.
Continuity mistake: In the plane, Willie wakes up Indy, who asks if they've arrived, and a feather lands on his head. A frame later the feather is gone.
Continuity mistake: On the bridge, an arrow suddenly appears to the right of Indy's foot seconds before any arrows are shot at him. (01:42:55)
Continuity mistake: When Indy is fighting the Chief Guard on the conveyor belt, there is nothing behind the guard before he picks up the large rock, but in a close-up there are now small rocks on the belt.
Continuity mistake: When Indy hangs the assassin on the fan, in one shot he's spinning, but in the very next shot he's not. He can't just instantly stop, he'd have to slow down.
Continuity mistake: When Indy punches Short Round, he starts falling forwards, but lands on his back.
Continuity mistake: When Mola Ram is climbing the bridge, Willie and Short stand together; half a second later Mola Ram falls and Short has managed to climb up and move apart to let him pass by. Then a nano-second later, Mola Ram grabs onto a piece a wood and Short and Willie manage to stand together again. (01:41:15)
Chosen answer: His neck was snapped by the whip getting caught in the fan. There isn't always blood with a hanging. Since the fan wasn't designed to hold a man's weight, the motor in it would have stopped or given out.
Captain Defenestrator