Continuity mistake: Near the end when Kate Capshaw, Harrison Ford, and the kid are on the bridge, Harrison cuts the bridge with a large sword. Several men fall into the water below. The bad guy grabs hold and hangs on to some of the henchmen. The number of henchmen changes between shots. Close-up 3, wide shot 2, close-up no men, then back to 2 and so on. The bad guy throws some off as he climbs up the bridge but the number changes in the wrong order.
Continuity mistake: On the bridge scene Indy's sword changes. Initially, he has a sword with a straight blade and no hilt; however, when he shouts at Mola Rom, he has a something like a cutlass curved blade and heavy handguard to a machete-like weapon he uses to cut the bridge. (01:38:05 - 01:38:55)
Continuity mistake: When Indy fights the two guards before the bridge scene, the sequence is all off. He knocks one to the ground, who lands still clutching his sword. The other one has his sword whipped away from him - it flies over the cliff, and he runs off, whimpering. We then see the other guard approach, and suddenly Indy's standing over an unconscious guard by the boulder and clutching a sword, both of which have appeared from nowhere. (01:37:25)
Revealing mistake: After Indy escapes from the conveyor belt, he runs on some suspended planks while being shot at. Watch the planks: There's black masking tape where the explosives are (which disappear in later shots). Furthermore, right before he takes out his whip, he grabs a railing where the bullet has just hit, and you can see that the black tape is dangling loose after the spark.
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.