Audio problem: As Radar sets the clock back to 4:30, you hear ticking. The clock is electric, and wouldn't make a noise like that.
Audio problem: Toward the end, after it's determined that Radar isn't the baby's father, there is a vehicle horn honking. When the camera shot goes outside, the sound of the horn is a few notes higher that when heard inside.
Audio problem: In Blake's office, he's talking to Hildebrandt about Klinger, and the camera does a close up on Blake. You hear him say "Of course", and his mouth is moving a little, but not forming the words.
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 ★