When Kelly and Jill "borrow" a cab, the cab is a Ford Galaxie. When they are passing Charlie's cab, the cab they borrowed changes into a Mercury Montego and stays a Mercury Montego until it is destroyed.
During the initial attack on Kelly, a long shot of the window shows the machine gun bullets completely shattering the lower left pane of glass, but in the following close-up looking through the window at Kelly, that pane is only partially shot out.
After Charlie's cab is hit by a truck the driver backs up to take Charlie home. After the bomber is caught, Kelly and Jill turn to see Charlie's cab turn around and leave. Even though the cab had hit a truck, there was no damage.
When the hit man exits his car at Charlie's mansion, the camera operator is visible - reflected in the car door.
Bill is shown working at the West Covina Police Department, but the building used for the establishing shot is Santa Monica City Hall.
A lot of plot holes here: as soon as their window is shot, Jill starts screaming for Kelly out the window and proclaiming that "Sabrina is dead". 1) How did she know Kelly was down there, without checking first? 2) She had no time to check for a pulse to confirm "death".
Kelly says someone fired a "rifle" into her bedroom even though it was clearly a machine-gun attack of dozens of rounds in five seconds. (Later, Sabrina states that it was an Uzi.)