Visible crew/equipment: During the montage of the kid, there is a shot looking in from the front of the car (featuring Dick Tracy and his girlfriend, with the kid in the middle) where the back window is just a blue screen, and the black stage curtains (behind the car) are visible at the top edges of the screen. (00:26:30)
Other mistake: When Big Boys' men drive through the garage door trying to escape, Dick Tracy, the cops and the goons start opening fire. Yet, nobody seems to feel the need to stop and reload their weapon. They just keep firing without ever running out of bullets.
Continuity mistake: Dick Tracy and Kid narrowly escape the exploding boiler at Tess' apartment building. They leap to the ground a second before it explodes. As the dust settles, Tracy pushes himself to his feet - to reveal explosion debris that was already underneath him.
Continuity mistake: When Dick Tracy is interviewing Mumbles, he fills a glass of water right up to the rim. When he offers it to Mumbles, the water level has dropped by half a centimeter, but when the shot goes back to Tracy, the water level is back up to the rim again.
Revealing mistake: When the goons are taking Tracy to the rendezvous with Big Boy, the Kid jumps onto the back of the car. As he does, the small platform he is to ride on is very discernible.
Revealing mistake: When Big Boy is announcing his take over after disposing of Lips, the line between the prosthetic chin and real skin is visible in the profile shots.
Continuity mistake: The red can that got crushed and was lying ahead of where Tess was tied up disappears after Breathless dies and Tess is freed.
Other mistake: When on the ledge before Spuldoni is killed, Tracy answers his watch/radio. Trouble is, his right hand never leaves the building to push the button so he can talk.
Revealing mistake: In the shootout of the escaping cars, inside the second car, you can see roll bars in place for when the car rolls over and hits the parked yellow car.
Continuity mistake: In the boiler room, after the thugs leave, Tracy looks left and right at the steam. His hat swaps from tucked in to loose and lifted up between angles.
Continuity mistake: In the boiler room, when Kid is freeing Tracy from his ropes, the amount of steam around Tracy suddenly decreases to barely zero when the angle is focused on his back.
Revealing mistake: When Tracy and Kid escape the explosion, the stair and rail wobble, revealing they're a prop.
Continuity mistake: When Tracy is tied up in the basement, the rope around his body changes styles between shots.
Continuity mistake: Big Boy tries to bribe Dick Tracy in the basement of Tess' apartment. He drops two wads of loose bills on the table in front of Tracy. Cut to Tracy asking Big Boy if he is "gonna put all that money down". When the camera angle cuts back to Big Boy the loose money has disappeared and Big Boy drops wads of bundled money on the table. Cut back to Tracy refusing the bribe and he is gathering loose bills off the table to throw at Big Boy.
Answer: He was babbling like an idiot, he was trying to justify his actions not only to Tess but himself. The "I love you so much I have to kill you" defense.