Other mistake: Clarence tells George that his brother died at the age of 9 because he wasn't there to save him from falling through the ice, but when you see the tomb stone, it shows Harry Bailey was born in 1911 and died in 1919. That would make Harry only 7 or 8 years old.
Other mistake: Marlowe fires several shots at Art Huck and Lash Canino but if you look at the chamber when he takes the gun out from under the dashboard, there are no bullets in it. (01:41:45)