When Harry Angel impersonates an official (Harry Conroy) from the National Institute of Health at the private hospital just outside Poughkeepsie, at the end of his conversation with the nurse, his glasses disappear between the penultimate and final shots of the scene.
After Harry finds Dr. Fowler dead, he lights a cigarette and the camera shows a close up of the gun in Dr. Fowler's hand, not fully grasped, pointing towards the left side of his body. In the next shot Harry goes to grab the Bible with the ammunition inside, and the gun is now pointing up towards Dr. Fowler.
When Harry tries to avoid Ethan Krusemark's two goons by buying oysters he ends up on the floor being attacked by their dog. If you look carefully you will see that the oyster sellers hat appears and disappears off his head from one brief shot to another.
At the end of the film, it is implied that Harry Angel was executed for his murder of Epiphany Proudfoot. Yet, it is highly unlikely that a white man in 1950s Louisiana would ever be convicted in a state court for the rape and murder of a black girl, much less put to death for it.
When Harry is running from the goons chasing him, he interrupts a street procession. As he knocks a few people to the ground, you can see that they're wearing knee pads, especially the woman in the skirt. As this woman lifts herself off the ground, you can see her black knee pads.