Character mistake: At the FBI facility, Agent 11's handler buckles the collar on the dog's neck. Later, when Gordon has put the collar on and tries to get it off, he's trying to pry it off. He just buckled it on not two minutes earlier. He's stupid, but not that stupid.
When Stephanie (the kid's mom) gets sprayed with mud by the bus, it is accelerating as much as it can in reverse. Why would it accelerate so much in reverse if it's trying to avoid falling down the hill?