When Mary Grant runs across the street on her way to the bank, there are no cars parked along the road. In the next shot, a blue station wagon is now parked behind the police car.
The innocent victim of an altered check is not responsible for the altered amount.
The gold Mustang with white top crew car can be seen behind Adam-12 as Malloy and Reed turn onto Riverside Drive from Forman Ave. It has its flashers on, likely blocking any possible traffic that approaches from behind.