When Kahu asks Ricky about his mom, he picks the photograph he's got of her from his pocket, and it is unfolded. The shot cuts to Kahu receiving the photograph while being folded, and then unfolding it again.
When Ricky sees the 2 officers in the woods, he does not have a rifle. In the next few shots, Ricky alternates between having a rifle and not having one.
When Ricky goes for help for the ranger, he does not have his rifle. He comes back without the rifle and looks for Hec. Then he shoots game with the rifle. When he finds Hec, Hec has both rifles.
Realistically, Ricky Baker would have lost a significant amount of weight when himself and Uncle Hec go on their trek into the bush: They would have been surviving on little food and doing a lot of exercise every day.
In the final chase with the cop cars the audience see they are ford falcons. The New Zealand police force don't use Ford falcons in their police fleet. In fact they use Holden Commodores which is the rival to Holden in New Zealand.
Ricky's dog attacks a wild boar by biting on its rear left leg - which then bends at a knee, revealing that this huge beast is just a man wearing a costume.
Hec and the boy have been out in the bush for about 6 months, but their hair, and especially Hec's beard, have not grown.
No kiwi Hunter worth his salt would kill a pukeko for eating - they are notoriously bad eating birds, hence the cooking joke: boil a pukeko with a shoe and when the shoe is soft, throw away the bird and eat the shoe.