Note: Unlike several other slip ups incorrectly entered under the movie title "Rambo" but actually refer to "First Blood" this slip up actually does take place in the latest Rambo movie.
When Rambo is taking the group of missionaries along the river, one of the guys tells Julie Benz's character not to talk to Rambo, but she does anyway. Rambo is kneeling at the back of the boat steering. His right knee is on the deck, with his left leg bent & left foot flat on the deck. The camera shifts to a close up of his face. At no time is he seen shifting his weight or moving his body. Yet when the camera goes wide again, his legs have swapped positions...his left knee is now on the deck, with his right leg up & bent. There's no way he could have swapped knee positions without a significant & obvious shifting of his weight.