Comrades in Arms: Part 2 - S6-E13
Audio problem: When Hawkeye and Margaret are being driven into camp, everybody is cheering. Watch the driver of the jeep. He hits the horn button a number of times, but the horn is never heard.
Audio problem: After Potter convinces Saunders he still wants to live, the hiss from the anesthesia machine fades out even while Potter and Saunders are still standing next to it. Neither Potter nor Saunders turned off the valve again.
Audio problem: As Roy and Loraine enter the camp, you hear a "YEE-HAW" from Roy, but if you watch his mouth, you see he really says "YAHOO."
Answer: Even an Army field hospital would have SOME weapons for self-defense if the enemy attacked. What's meant is that it's not a combat outfit, and therefore wouldn't have enough weapons to actually attack anyone. (It's also mentioned a few times that the Officer of the Watch is supposed to carry a pistol at all times, but Hawkeye refuses to do it when he's in charge and Colonels Blake and Potter don't enforce the rule).
Captain Defenestrator