When Steve and Garth are climbing the cliff, Steve had no visible protective gear, but after Garth slips, Steve is wearing aviator-style safety goggles.
When Steve falls while mountain climbing, he lands on the ground with minimal shrubs. In the next scene there are shrubs about one foot high and the mountain looks different.
The plane was supposedly buried for decades and then uncovered by an earthquake, yet all around the wreckage is green vegetation which couldn't have grown under whatever covered the plane. If the plane had rolled there from a higher location it would have been surrounded by the debris of whatever had covered it.
Obvious stunt double when Steve Austin kicks a man off his horse.
Steve and his Asian guide jump alone, with just their equipment bag on the third parachute, yet in the wide angle-shots of the three chutes seen against the sky (these shots of shiny silvery parachutes floating down are re-used in at least one subsequent S.M.D.M. movie, too), there is clearly a man riding down on each of them.