The appearance of King Kong in the film keeps changing due to different suits being used for different scenes.
During some of the North Pole scenes in the film, Dr. Who's men cast shadows on the painting of the "distance" (mainly snow-capped mountains) on the studio set.
When fighting Gorosaurus, the King Kong suit is very clearly falling apart. At one point in the film, when Gorosaurus throws King Kong off of himself and King Kong flips over, part of King Kong's neck "peels off" and you can see the suit actor inside.
During his fight with the Giant Sea Serpent, King Kong does not even once close his eyes despite all the sea water splashing into them.
When Mechani-Kong is on the platform to be elevated at the beginning of the film, it does not have the bombs on its waist. In the next shot when it is above ground, the bombs are attached to its waist.
In the film, Dr. Who is trying to get Element X by digging into the land under the ice at the North Pole. There is no land under the North Pole, but there is a lot of it under the South Pole.