When the Toa race to the island, the ones who have gone ahead are missing from view in a number of shots.
Onua raises an earth bridge to get to the island and Ketar passes him as they walk. But in the shot when Kopaka lets go of Lewa, both the bridge and Onua are gone from the background, and Ketar is still standing on land.
After Pohatu throws one of Umarak's doubles off himself, a slab of rock appears beside him when the shot cuts.
In some shots, the chains hanging from Umarak's armor aren't animated when he moves.
When the Toa and Creatures descend into the valley, their shadows disappear before the shot cuts.
When Umarak's doubles pop up, the dust cloud of the one to the left overlaps the tail of the double that's closer to view.
Inside the labyrinth, the flying Creatures move in unison with the giant floating stone blocks, and stop in the air when said blocks also stop moving, then continue flying forward again after a pause. Shouldn't they keep flying forward in one uninterrupted motion, considering they're not actually touching the blocks?
It takes a long time for Gali to interpret the ancient inscriptions and realize the Toa have to stand on the symbols on the ground. Considering these symbols clearly refer to the Toa and correspond to their colors to boot, wouldn't it have been immediately obvious that that's where they need to stand without having to decipher the writings?
Umarak has to steal Ketar from Pohatu and forcibly combine with him to open the sixth gate leading to the Mask of Control. Why didn't he simply go through any of the five gates that were already open? The dialogue suggests that all six of the Elemental Creatures are needed to free the mask from the crystal it's encased in, but that is not confirmed, and Umarak simply smashes the crystal to get the mask. The importance of having to take the six Creatures through the six doorways is not explained.