Continuity mistake: When Lieutenant Willis wakes up in the Swamp and puts his shirt on he's wearing his dog tags, but when he tosses the papers and puts on the rest of his clothes the dog tags have suddenly vanished, then they reappear, vanish, and reappear again.
Continuity mistake: When Frank walks into the Swamp and puts down the typewriter, in shots facing Frank the manila envelope's open flap faces up, but in shots facing Trapper and Hawkeye while they're pretending to argue the envelope is flipped over with the flap facing down, then when Frank walks back to the envelope the flap faces up.
Continuity mistake: While Trapper and Hawkeye are lying on their cots, one by one everyone joins them in the Swamp, and in Trapper's closeups the "USA sterilized" that's printed on his pillow is upside down, but in the wideshots his pillow's flipped over with the print right-side up.
Continuity mistake: While Radar and Hawkeye are in the mess tent, after Hawkeye cracks a joke about how the cook sculpts grease into the shape of lamp chops, between shots facing Radar and the shots facing Hawkeye we see Radar either holding bread in his right hand or a fork.
Continuity mistake: When Trapper and Hawkeye are sitting outside the Swamp, Hawkeye pours the martinis from the tall glass beaker, and in the shots facing Hawkeye there are quite a few large ice cubes in the beaker, but in the shots facing Trapper there aren't as many ice cubes floating in the beaker.
Continuity mistake: After Lieutenant Willis wakes up in the Swamp he gets dressed and puts his tie around his neck with its tail end on his right, but when it cuts to his closeup the tie's wide end is at his right side, then it switches again.