Peter and Alice, invited to attend the charity event, can be seen sitting at their table at the party before they even entered the room.
The Polaroid which terry examines with a magnifying glass shows Peter smiling slightly. The picture Alice & Janice look at has his mouth closed in a grimace (the plot makes an issue of why he isn't smiling in the photo).
In the final scene, when the helicopter is returning from the retrieval mission, Meg walks up to greet her husband, and she has a huge fever blister on the right side of her upper lip. Later, in that same scene, the fever blister disappears.
Even though the movie takes place in a fictional South American country, the Ecuadorian flag can be seen flying in many places.
Bowman empties his gun and the slide stays cocked back because it's empty. In the next scene the slide is back in position, but Bowman wouldn't know how to do this to a gun, having not used one before.
Bowman speaks into the wrong side of his Nokia 9110 Communicator.
Alice slaps Thorne's left cheek, but when he walks in to the house, he is massaging his right cheek.
The ferry's position in relation to the overhead bridges changes when Terry is traveling on the river Thames, talking to his superior.
When two ELT soldiers fly into the air after Thorne detonates a claymore mine, wires are visible aiding the stuntmen.
The grenade Dino throws into the hut is a noise/flash distraction device, commonly called a "flashbang." Flashbang grenades do not detonate and fragment like antipersonnel grenades, so it would be normal to see the spent grenade body lying on the floor.
When Peter is photographed by his captors, his feet are completely red, covered in blood. Then when the instant-photograph is being looked at in the hotel room by Terry, Alice and Janis, there is less blood and injury visible on his feet.
Right before the shot of Peter Bowmen stopping his car at the roadblock he is wearing sunglasses. In the very next shot, you can see in the rearview mirror that he is not.
The marching band drummer, while standing in front of the grandstand.
There's a red bucket visible when Peter and Kessler work in the camp, just before Peter grabs the map. It changes position and even vanishes briefly.
When Terry, Dino and the others approach the guerilla camp, takes with rain and without rain are mixed up.
When the rebels arrive at the camp with Peter in their midst, you see the guy with the yellow shirt, Alex, as his fellows help him to lie down on a table. A short while later Alex arrives at the table, helped by his mates. And later still we see him dismount the mule.
Towards the end when Terry and Alice are kissing, Terry is holding Alice's head. When the camera swings to the other side, Alice is holding Terry's head.
When Kessler is standing at the top of the waterfall (shown in a long shot), he clutches at his injured shoulder. However he has not been shot yet. He gets hit in the shoulder during the next (close-up) camera shot.