When Harry is held captive with his hands tied behind his back in General Midwinter's firing range, his glasses are on when he is standing up, disappear when he is sitting down but re-appear when he stands up.
After being freed from detainment, Harry Palmer attends the end of a symphony concert, which is supposed to feature Dmitri Shostakovich's "Leningrad" Symphony, written in 1941 during the siege of Leningrad by German troops. What we hear, however, is the end of Shostakovich's 11th Symphony "The Year 1905". Yet, music from the "Leningrad" symphony is featured later on during Midwinter's speech to his soldiers in Finland and during the final battle on the ice.
Palmer is seen signing the Official Secrets Act in the car as he's just been re-assigned, after retirement. Civil Servants in fact, sign this just the once on first acceptance and are bound for life. They do not re-sign for specific tasks or missions.
When the virus-loaded eggs are examined in the secret lab they are extracted from an egg with the yolk. Viruses when bred in eggs do not reproduce in the yolk but in the cells of the living chicken embryo.