Factual error: Dirk is fighting on top of the solar plant with the guy who attacked Eva at the start of the film. Dirk shot him in the hand with a spear gun. It doesn't matter how tough the guy, is he would not be able to hit Dirk with that hand without being in excruciating pain.
Continuity mistake: At the end of the film the waiter/agent serves up a glass of bottled water and gets in the lift, once in there we see him remove his bow tie but when we see him go down in the lift he's wearing the bow tie.
Continuity mistake: When Rudy shows up to the dirt house with the other guys after the Panama boat scene he walks in barefooted. As the shot goes back to include his feet he magically has sandals on. (00:46:11)
Other mistake: After Dirk, Al, and Eva jump from the camels to the train the camels are seen practically huddled together when noticed by the guard even though each camel traveled further than the last one.
Answer: So they will not discover the poisonining that is going on.