Audio problem: If it is raining, like in the Halloween event or other random storms in the game's time cycle, the audio can change in structures you're inside. But the rain follows the rules as well, like if you're in a tunnel, the rain doesn't fall inside the tunnel. However, if you get inside a bus that is in that tunnel, suddenly you'll hear the sound of rain hitting the roof of the bus, despite there not being any rain that can hit it.
Revealing mistake: When you get the random encounter of Richie, he will start speaking. When he's closed to finished, suddenly his mouth will stop moving with his words for most of what he says, but then start again at a few sentences, only to stop again.