Other mistake: During the Tri-Motor crash sequence, the crew dumps the fuel from the aircraft and bails out. In the shot of the red fuel pouring out, the fuel is shown streaming out of the exhaust pipe for the center engine, which would be hot enough to cause the fuel to ignite and either set the aircraft on fire or cause it to explode.
Other mistake: In the "tunnel of bugs" you may reasonably expect there to be such creatures as cockroaches, spiders or giant centipedes, but the majority of the insects are locusts which are herbivorous and would not be found in an underground tunnel. Other out-of-placers are giant stick insects (also herbivorous) as well as a South American harlequin beetle (this part of the film is set in India). You can also see, in the scene where Willie turns her hand over to reveal one of the giant stick insects, that she is cupping it to hold the insect in place.
Other mistake: When fighting the sword wielding guards before getting on the bridge, Indy uses his bullwhip to disarm one of them. As the sword flies out of his hand it kind of hangs in the air as it falls. It is obviously a prop made of a very light material. (01:42:35)
Other mistake: When the airplane Indy and company are flying in runs out of gas, there is a close up of the instrument panel. The hands of the altimeter start spinning as the plane descends. However, so does the altimeter setting at the side. The altimeter setting is changed by the knob at the bottom. It does not change with altitude.