During the snake dances, the cobra is an obvious puppet in the long- and medium-distance shots and a real cobra in the snake-only closeups.
How did the chimpanzee travel from the mainland to Cobra Island?
The boy, Kado swings on a rope that is attached to a nearby building (c. 41 minutes) to gain entry to the dungeon. He then uses the same rope to swing to the dungeon floor. How could he have untied the rope?
Taking a small boat to travel to Cobra Island and then leaving it to drift, a short distance away from the shore, before transferring to a rowing boat is illogical. Furthermore, when the rowing boat is beached, it it left far too close to the waves to avoid being swept away to sea by the tide.
At the start of the film, Tollea's wrist is shown in close up with the two bloody cobra fang-marks visible. In the next, slightly longer, shot no such marks are visible.
When the rowing boat is beached its large pair of oars are not visible.