Other mistake: As the Governor looks at the gorilla sentries, he is looking about forty-fiveĀ° across the aim of the cannon next to him. When the cannon is fired at the gorillas, they are directly downrange of the cannon. After they're killed, he's again looking across the cannon's aim.
Continuity mistake: As the two gorillas watch the approaching humans, one gorilla raises the telescope, then after the angle change, raises it again.