The necklace Lucien puts on Dennis' neck before he got poisoned changes the positions between shots. However, in a lower position from back view, higher position from front view.
When the Duvalier government is overthrown, it is stated to be "in the middle of the night", yet news reels show cheering crowds outside in the daylight in the middle of the day.
The movie mistakes the Cane Toad (an amphibian, bufo marinus) with the Sea Toad ("crapeau de mer") which is indeed a puffer fish.
Just before the spider starts crawling on Dr. Dennis Alan's face, you can see the crew member in the left background who placed it there.
At 12:35, apparently from somewhere outside the set, an ambulance can be heard driving by with its siren on. This is most noticeable in modern day digitally enhanced versions of the film, such as those available on streaming.
At Captain Peytraud's first meeting with Dr. Alan, Peytraud wears his full Haitan Tonton Macoute uniform including a row of several award ribbons. All of these ribbons are in fact United States armed forces decorations - clearly visible are the Vietnam Service Medal, Korean Service Medal, Air Force Overseas Ribbon, and the Army Good Conduct Medal.
At about the 1:05 mark a computer screen shows the word "specimen" misspelled as "speciman".