Early on Mrs Peters tells the crew from the boat that the diamonds were stolen from a temple. Later someone says that the mausoleum was built by the Europeans who mined the diamonds. An African pagan temple would not likely be built by Europeans.
The first freighter seen on screen has two masts. But when we look back again, it now only has one mast.
One character says, "50% isn't hard to resist." He really means either, "50% isn't easy to resist," or " 50% is hard to resist. "
Throughout the film Jan and the other characters, including Grandmother Peters, repeatedly refer to Mrs. Peters as Jan's grandmother and Jan as her granddaughter; but when Grandmother Peters greets the members of the expedition upon their arrival by boat, she introduces Jan as her "great-granddaughter".