When Declan is driving Beck into El Dorado, they stop for a truck full of rebels and Declan explains who they are. In a close-up of Declan, his mouth is moving but he's saying something completely different from what we hear.
In the final fight scene between Beck and Hatcher, you notice that Hatcher has no bullet wounds on his shirt sleeves. When Mariana shoots Hatcher in his right arm, he grasps his bicep. However, the "bullet holes" in his shirt appear near the elbow. Also, Beck shoots the pistol from Hatcher's right hand without hitting his body. In subsequent scenes during Hatcher's final dialog, Hatcher's shirt has an identical wound on his left arm, with no one having shot him.
When Beck has hit one of the bad guys with the two shotguns he then grabs one of them and puts them through his arms and then cocks them. He then pushes the guy forward into the other guy but on the next view of the same action the guns have turned around with the barrels pointing behind him.
When Beck is talking with Travis' Dad, the Dad has a cloth on his shoulder. Firstly the cloth changes in position from shots but also in one shot he hasn't got it on, then in the next it's back on again.
When Beck, Mariana, and Travis are in the boat and the camera changes back when Mariana looks at Travis and the camera pans down to the side of the boat you can see a board attached to the boat. Which is what the used to keep the boat from rocking. As you notice when Beck, Mariana, and Travis all move the boat never rocks back and forth like a boat should in the water when someone moves.