Continuity mistake: When Blofeld is just about to shoot Bond with a Webley & Scott Mk. IV revolver in .455 Webley caliber, Blofeld's hand is hit with a ninja throwing star. However, the gun he drops isn't the Webley, but a Smith & Wesson .38 Special.
Visible crew/equipment: As Quatermass drives back to the spaceship in a cab, just before it is to be drilled, the film crew can be easily seen in the cab's windows. A woman with a white cap can be seen holding a script. Later when the police use a megaphone on their car to announce the spaceship is a hoax, you can again see the same woman with a white cap in one of the windows of the police car.
Suggested correction: How could you tell if the reflection showed the actual film crew and not just a TV and newsreel crew assembled for the scene? They were also using mounted cameras and carrying papers.
Continuity mistake: At the beginning, the scientists are told they are being sent to study the strange fact that seven meteors landed near each other in a V formation. The government agent even traces a V on the board with his finger. When they get to the field, panoramic shots show that there are nine meteors, and they are in a 3 by 3 grid, not a V.
Revealing mistake: In the scenes inside the space capsule, as Roy goes through the sequence, the wires holding him up in the floating sequences, and the crackers when trying to eat, are visible.