None of the natives of the foreign country have any accents except the rebel leader.
At the end of the car chase, when Mannix and his two passengers exit the car and are stopped by the rebels, in the wide shot, the woman is standing behind Mannix and the doctor. Then when the camera switches to a closeup of them, they're standing side by side. Then when the camera switches to a wide shot again, the woman is once again standing behind Mannix and the doctor.
The aeroplane has two front windows on both the outside view and the front view, but viewing in from the front, there is but one front window with no crossbar in between the pilot's and the front passenger's side.
During the car chase a Jaguar XKE is seen with a California license plate, speed limit 8 MPH studio back lot signs can be seen, a "Bang the Drum Slowly" billboard can be seen in Mannix's rear view mirror. All wording in English and MPH instead of KPH, even though this is supposed to be a foreign country.
The Beechcraft Baron 95-A55 (N9750Y, s/n tc431) is an American registered plane. It is unlikely this plane would be seen in the foreign country used in this plot.