Factual error: When the CIA guys are 'invited' to the secret underground base via the highspeed drop platform - shouldn't they be flying off at the speed the platform is descending?
Factual error: This is more of an understandable error: In the movie, the Russians still use the AK-47 or the AKM; at this time, the Soviets had the AK-74, a small caliber version of the original AK with plastic magazines and a large but effective muzzle break. At that time, AK-74s were hard to come by for the American movie industry, though.
Factual error: Fitz-Hume and Millbarge shoot the rocket base crew with tranquilizer dart pistols. But the crew wear thick winter clothing, and air-powered darts should have trouble penetrating deep enough to deliver their load - and the serum would not take effect immediately for that matter (the guards drop as soon as they are hit).
Answer: Dan Akroyd was giving Chevy Chase the answers to the test, KGB was one of them.
JamesP