Jack presents Joan with a very elaborate necklace from his pocket. When she takes it in hand, it's a simple charm on a chain.
When Jack slides down the hill face first between Joan's legs, his shotgun is no longer in his pack. The gun reappears in the next shot.
In the first shootout with Zolo after the bus crash, Jack fires nine shots before reloading, then fires 11 shots (nine in the gunfight and two at the jeep). His Remington 870 only holds five rounds.
Joan's dress becomes clean when she makes a break for the old bridge.
When the bus crashes into Jack's Jeep, and all of the luggage goes flying off the luggage rack, Joan's blue suitcase pops open when it hits the ground, spilling her clothes all over the ground. However, when she picks her suitcase back up after Jack dispatches Zolo, her suitcase is closed again, with all of her clothes are still inside.
When the statue containing the emerald is retrieved from the milky pool in the cave, it is wrapped inside a bundle of fresh green grass inside a bag. If the gem had been under that pool long enough for a map and treasure hunt, the grass would not be green.
Sailboats are not trailered with masts raised and sails rigged.
Jack carries a Remington 870 left-handed shotgun, but he always shoots with it right-handed.
When Ralph is talking on the phone in the local police station, he notices his wanted poster. It appears to show only his first name. A closer look reveals that it says "RALPH (se desconse appellido)" which means "surname unknown."
When Jack grabs a vine to swing to the other side of the ravine with Joan, he hits a rock wall. Not only does the wall move slightly, it flexes once he hits.
When Joan and Jack are at the festival at Santa Catarina, Ralph is under a table, trying to steal Joan's purse. A closeup shows wooden table legs as he squeezes through. When the lady at the table catches him and pulls him to his feet to hit him, the table legs are metal.
When Joan exits her apartment for the first time, she turns the key counterclockwise to lock the door, but this would actually leave it unlocked.
When Zolo stabs the man in Joan's building, the man reacts before he is actually stabbed.
Despite drinking 2/3 of a fifth of Cuervo Tequila, and inhaling burning cannabis, neither Jack nor Joan act intoxicated (until Joan passes out).
When Jack and Joan are having a conversation from opposite banks of the river, there's no way they could hear each other over the roar of the waterfall and raging torrent.
When Joan is talking to the bus driver in broken Spanish, Zolo approaches and finishes her sentence by saying "Cartagena." Joan responds to this by saying, "Oh, you speak English!"
Hearing Zolo utter this single word, the name of a Colombian city, does nothing to suggest he speaks English.
Very near the beginning, when Joan is choosing a miniature from her cabinet, a crew member is reflected in the cabinet's glass door.
When Jack and Elaine drive into the river in the car, the retention cord attached to the front of the car, to keep the car from flipping onto the roof, is visible.
When the car goes over the waterfall, the stunt actor is visible standing on the side of the car, next to the closed door, and jumping.
When Joan's bus hit Jack's Jeep the wire moving the vehicles (underneath) to simulate the crash are visible.
Sulphur crested cockatoos are native to Australia, not South America.
Joan actually boards the right bus at the airport. The sign on the bus says "Castille San Felipe". This castle is located in Cartagena.
The alligators in the film are American alligators, found only in the southeastern United States, primarily the Gulf states, Georgia, and South Carolina.
The film is set in Colombia, but all of the Hispanic actors have a distinct Mexican accent.
After Juan and "Little Mule" have jumped the river, the following Jeep crashes and lands upside-down in extremely shallow water 20-30 feet wide (as evidenced by the shot of the jeep as it lands). Judging by the slope of both banks and the shallow water, the statement that the river is impossible to cross for 200 miles in either direction is simply not true.
Ralph surprises Jack and Joan in the cave after they find the emerald, holding a gun on them, but Ralph's clothes are dry. How did he cross the river and the waterfall without getting wet?
When Jack and Joan emerge on opposite sides of the river after jumping over the waterfall, Jack tells Joan to follow the sunset to Cartagena. The treasure is close to the middle of the Colombian Department (State) of Cordoba (reference when Jack learns about the map), so she would be heading away from Cartagena, which is north of Cordoba.
Joan asks the bus driver in English and broken Spanish if the bus goes to Cartagena, but he doesn't seem to understand a word. "Cartagena" should ring a bell.
Jack doesn't remove the plastic on the cannabis kilo bricks before burning them.
Jack never pronounces Cartagena properly in English, always saying "Cartagenia".
After Colton decapitates the bushmaster snake in the downed aircraft, Joan asks "Is it poisonous?" A college-educated professional writer would know that plants are poisonous and snakes are venomous.