Factual error: In this episode, the regulars receive and respond to letters from a Fourth-Grade class in Hawkeye's home town. Charles receives one from a little girl who says she's sent him a birch leaf. Unfortunately, the leaf he removes from her glassine envelope is a maple leaf. (Note: there was no indication that this was supposed to be her mistake.)
New this week Other mistake: Looking at the pins when Margaret bowls at the end, the 5 pin slides backwards towards the camera, but not fast enough to bounce off anything and then fly in from off screen. Granted this was done in slow motion, but the physics don't seem to add up.
New this week Continuity mistake: In Potter's tent, he holds the door for Brandy to enter. In the close up, you see him drop his left hand to close the door after she passes him and inside. After the angle change, his hand is back on the door, and she's just even with him walking forward.
New this month Deliberate mistake: BJ mentions to Charles that if they don't sign the armistice it will be the second time in 2 years and then he will miss his daughter Erin's second birthday. This is BJs 7th season and when he arrived at the beginning of season 4, Erin was already born, making it absurd that seven years later she could still be one year old. Because the real war lasted 3 years and the show 11, there are obviously some errors like this that can't be avoided but this was blatantly egregious.
Other mistake: Across the show, several times doctors looking at an x-ray picture say things like, "Looks like he swallowed a whole junkyard" or "His belly is full of shrapnel." In fact, shrapnel, being metal fragments, should show up as clear white spots on the x-ray pictures, but none of that is visible in any of the x-rays shown throughout the show.