When martin swerves to avoid the water sweepers, his car is wedged between a brick wall and a blue car. As Christine gets out of the car, the blue car is no longer there. After taking the green car and driving away, the shot of the men protesting shows the blue car back in its original position.
Just before being shot down the UNCLE airstrike helicopter suddenly became a Bell 47J-2A instead of the Bell 47G-3B-1 that it was.
The UNCLE air strike helicopter (1963 Bell 47G-3B-1) has a US registration number (N73962). Since this is taking place in Greece the registration would be something like SX-ABC .
When the helicopter was shot, a ball could be seen suspended from a cable as the flames and smoke disappeared. There were no helicopter wreckage parts visible. An explosive was probably dangled far below an actual helicopter for this filming.