They're driving a Series 2 Land Rover that didn't come out until 1958, yet the film takes place in 1951.
In the nightclub the African-costumed drummer is playing a djembe. Rather than holding it correctly, which is lower and, in most cases, between the legs, he is holding it under his arm like a talking drum. Also, the djembe had a high ringing sound whereas the sound heard is quite duller.
When the first day of shooting is interrupted by rain, the rain is created using a special rig, which is a common practice in film in order to make sure there's rain on schedule. During the shot where Lockhart talks about the rainy season, in the background it can be seen that the wet ground reaches a sudden end a few meters away, and beyond it everything is perfectly dry.
The film is set in Uganda where the main African languages are Swahili and Ganda. But the language heard on screen throughout the film is Shona, the main language spoken in Zimbabwe, which is where the film was actually shot. For instance, the racist hotel manager Harry shouts "Iwe!" meaning "You!" at an African servant, which is a derogatory way of addressing an inferior. Later when the boat is first seen as it's being hauled up a ramp, Lockhart is heard shouting "Donza!" which means "Pull!" At the safari camp, Zibelinsky addresses Kivu the chief hunter as "shamwari," meaning "friend," and he refers to Wilson as "mambo," meaning "chief." Kivu replies to a couple of their comments by first saying "tatenda," meaning "thank you," which in Shona is a polite way of acknowledging when a superior speaks to you.
The map detailing the crew's trip by plane from England to Uganda shows Germany with pre-WWII borders. The movie is set around 1950.
The plane's flight to Africa is marked from it's starting point in Europe, south to it's destination in Uganda. The shot then switches to the plane flying over the Victoria Falls, Zimbabwe.
When John Wilson is talking to Pete Verrill over breakfast he refers to him as 'Jeff', Jeff Fahey being the real name of the actor.