Factual error: Twice in the film it is made clear that the Pym particle works by reducing the space between atoms in order to shrink an object, and by increasing it to enlarge them. This means that the object will weigh the same, whether shrunk or enlarged - it cannot be otherwise. A 90kg man the size of an ant would punch a hole through any surface upon which he stood (and couldn't ride ants), Doctor Pym has been walking about with a 60 tonne tank in his pocket, Darren Cross lifts a full grown sheep between finger and thumb, and the supersized Thomas The Tank Engine would be far too light to crush the police car (in fact it would float harmlessly away as it would probably weigh less than the air it displaced).
Factual error: After the Scarlet Witch forces Banner to become Hulk, he goes berserk in Johannesburg, South Africa. A few minutes earlier they were near the ocean at a ship scrap yard. Johannesburg is many kilometres away from any ocean.