When Fitch and friends go through the checkpoint, Fitch tells Tiffany and the guy in back to disappear and that's exactly what they do - somehow Tiffany is able to hide herself in the front seat of the car without being noticed.
When Fitch and the others are getting briefed on their mission, Tiffany comes out to the deck with the "beacon" for Fitch. She's immediately inside with Barry Williams when they give the team the "Go" for the mission, switch to them running for the chopper and she's back outside again.
When Fitch and the others are ready to head out to the helicopter, Fitch says goodbye to Monroe (Tiffany) outside and she gazes onward. However, when cutting to the scene with Brady talking to Fitch via phone, Monroe is clearly visible beside Brady. Brady and the others are inside. The movie continues to cut back and forth for the entirety of the phone conversation, inserting clips of Monroe looking onwards at Fitch and the others outside. Monroe is visible in both areas at the same time.
At minute 10, when the conversation with the scientist and the special forces agent takes place at the exit of the airport, the plate reading 'PUERTO AYACUCHO' is hand written. During this conversation, at minute 11, the plate changes to a metal made one.
When the reporter is telling TV Land about the "hurricane" announced by the government (weather people tell us about hurricanes, not the government), she is supposedly in Florida but mountains can be plainly seen in the background (Florida is flatter than Ohio).
Several characters refer to the location in Venezuela as the "Amazon basin". The river, however, is clearly described as the Orinoco, which has its own basin and drains into the Carribean Sea; the Amazon basin is quite separate and drains into the South Atlantic.
After the American warship bombards the piranha infested water, we see the characters test a lake. Whilst there are numerous dead piranhas floating in the lake, ducks can clearly be seen swimming. Ducks are impervious to warship missiles now?
In the end scene when Fitch finally blows the head off one of the piranha, the other piranha continue to circle the dead fish and are supposedly eating it and each other. However, the decapitated fish never seems to get smaller and none of the other fish are being attacked, despite them showing the scene several times.