Continuity mistake: When Po is killed by the NVA it is the middle of the night, Captains Cahill and Doyle are close enough to the village to hear the shots and rush back to the village but as they enter the village it is early dawn.
Continuity mistake: Preparing the crate for Bo-Tat's second airdrop In the beginning of the scene we see A.J (the black guy from the 101st) putting on a welding mask, the very next shot we see Farley (the white guy not from the 101st) is shown welding while A.J (who is now wearing his steel pot again) stands by watching.
Continuity mistake: At the very beginning of the movie Capt. Doyle is being air lifted to the village when the pilot tells him, "We have to take the scenic route." His door gunner immediately tightens his seat belt because he know the pilot is going to do some aerobatics. In the next shot while the helicopter is taking ground fire he stands up and returns fire without ever loosening his seat belt.