Plot hole: In a tape home, Winchester implores his father to get him out of the MASH and suggests that Senator Griswold should help as his father "paid good money for him". As the length of time the show ran so exceeds the length of the war itself, inconsistencies for dates are perhaps unavoidable, and it might not be fair to call them mistakes. In this case however, the writers/producers have carelessly picked a senator who only served from November 1952, making dating inescapable. As Charles, in the same episode, complains how hot it is and everyone is in shirtsleeves, it must be very late spring, perhaps May, at best, just a month before the end of the war. To emphasize the mistake, by the next episode it is late fall/early winter.
Other mistake: After pulling out of the camp to head for the cave, the bus is shown from several angles. Even though it's loaded, the shots of it travelling are re-used shots from an earlier episode, and the place it stops is a re-used shot from the episode "Rainbow Bridge"
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Revealing mistake: As Hawkeye calls for quiet in the officers' club, Henry pulls the tonearm off the record player, it comes away trailing a long wire behind it. Why would it even have a long wire to trail? After all, wire costs money too. It's not like the tonearm is designed to come off and be used remotely. My guess is: they lengthened it, so the shot could be taken several times without repairing the record player every time. Now, WHY they would do it that way and not simply use a dud record player is beyond me.