When Noa and Mae last meet, she hides a gun behind her back and then, ten seconds later, with both hands takes the pendant he offers her. But her tunic has no pockets, and as it is knee-long, it would be impossible for her to stick the gun in her trousers surreptitiously before holding out her empty hands.
An electrical generator, like the one seen in the silo, would not be functioning after "several generations", which is at least over a century if not several centuries. The lights would not function either and it is doubtful any of the computer components would be operable as well due to decay.
Raka would have needed a larger horse to carry his body weight.
Sylva is using an electric shocker to electrocute Noa, but since Noa is holding an electrical conductor (the electricity tower beam or cable) with both hands, there is no potential difference, much like how birds remain unharmed while perched on high-voltage wires.
Whilst AC current does cause extended muscle contraction a DC current is more likely to cause a large spasm and throw the recipient away from the source.
When Noa is being electrocuted by Sylva while hanging on the metal cable, Noa uncontrollably lets the cable go and falls down. In reality, when under the electronic current, muscles on contrary contract and Noa would not have been able to let the cable go until the electrocution is over and losing his consciousness.
After the grassland "hunt" sequence, When Raka, on horseback, strikes a chimp with his makeshift club, it makes a distinctly metallic "clang" sound, but the club is wooden; an uprooted small tree and its rootball.
When the bunker floods, the water is above the level of the ocean and somehow draining from a floor above the apes despite their floor not being flooded.
It's doubtful the apes would retain sign language after several generations if they are all capable of spoken language. There's very little use case for sign language, except maybe when hunting in silence.