Other mistake: When Callahan meets Sunny in his apartment lobby and she asks him, "What does a girl have to do to go to bed with you?" Callahan replies, "Try knocking on the door." and if you look behind Callahan at the Trolley going down hill, you can see a kid waving to the camera.
Other mistake: The vigilante bike-cop slaps a supressor on his Colt Python. A suppressor on a revolver doesn't work without serious modification. There's only one revolver I know of which would be able to use a suppressor, namely the Russian Nagant M1895. And that's due to the gas-seal system in the cylinder, which seals all the out-gassing, only letting the gases out the muzzle-opening.
Other mistake: In the scene where the mob boss gets interviewed in the garden atrium after being freed, the news media pushes up to get really close to the podium. Note that the first reporter, dressed like Gilligan, trips and almost falls into the podium. He catches himself but has to keep his head down during the rest of the shot.