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.
Other mistake: Many times during the series, soldiers are around the OR carrying a loaded weapon (magazine attached for example), when there is a sign outside the entrance that says "all weapons must be cleared before entering the building" or similar.
Other mistake: In all the opening sequence of each episode, a group of people are waiting on the pad to get the wounded off the choppers. If you look closely as the group goes to move, Mulcahy is there, but it's George Morgan, who played the role in the pilot episode. From the third episode on, it was played by William Christopher.