Continuity mistake: When they are talking about taking Sophie for a walk, Roy is sitting on the bunk. His captain's bars & medical insignia are on the wrong sides. After he stands up, they are on the correct side.
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: The C-42 was a military variant of the Douglas DC-2. Very few C-42's were built, so it's questionable that Potter would specifically have seen that particular model, but, given his military background, it's not entirely unreasonable that he might use the military designation even when the aircraft in question is actually a civilian DC-2.
Tailkinker ★