Continuity mistake: When the three heroes arrive at the village there's not a single bit of grass around. When they leave the place the morning after there's vegetation everywhere.
Continuity mistake: During the fight on the conveyor belt in the mine, the buckets and huge rock used to defeat the bearded giant keep changing positions all the time.
Continuity mistake: Indy's raft lands on the water, and he is ducking but rises up and rows with his hands for a couple of seconds. Then a frame later he is still ducking and rises up again.
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)
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)
Chosen answer: It was actually George Lucas who wrote the story, made it a prequel, and has stated it was because he didn't want the Nazis to be the villains again. The idea most likely seems if it wasn't a prequel, the Nazis could still be after Jones, even in China or India. But alas, there is really no other insight as to Lucas' prequel decision.
Bishop73