During the very last scene in "Dutch", when Dutch shoots Doyle in the backside with his airgun, the sound you hear sounds somewhat like an airgun going off, but then a split second later you hear the unmistakable metal "clinking" of a spent shell casing hitting a concrete, tile or otherwise hard surface.
As Doyle and Brock discuss Doyle's problems with his mom and Dutch; the camera cuts back and forth between their place in the backseat while they converse and Hailey trying to steal Dutch's ring. Throughout the cuts, Brock and Doyle's dialogue plays over the scene, but during shots of Hailey and Dutch, Brock can be seen in the back seat not saying a word and either staring into space or watching the action in the front seat.
When Doyle is riding in the back of the car and talking to the prostitute, shots of Doyle and the prostitute show many lights and other cars visible through the rear window. Shots through the front window of the car show an unlit, traffic-free road ahead.
When Dutch kicks his leg and falls onto his back, he turns over revealing he has split the crack of his pants. You can see his underwear are white (there's even a light blue car in the back-round to see the difference), then when he moons Doyle at the end of the scene his underwear is light blue.
When stopped at the gas station, the one hooker says to the other, "Brooke, do you want to wake up your friend?" Moments later, Doyle says, "I'll come in with Brock." Her name is also listed as Brock in the closing credits.
In the car trip at night when Doyle and Dutch are arguing over the radio, the power window and power seat switches are in the wrong position on their car. The Lincoln Town Car had these switches on the front doors, not on the center console, as these cars were six-seater cars.