In one clip of the soapbox derby, the three cars are in reverse order, left to right.
In the shootout between Danny and Tommy Banks, Danny fires twice and two bullet holes show up in the wall near Banks. A few seconds later, when Danny moves to another spot for cover, he fires again. This time, the same wall now has no bullet holes, three gunshots are heard but only two bullet holes show in the wall.
In the fight scene Danny has a bloody mouth before he was hit, then when his face is pushed against the mirror after the camera angle changes he is several feet away from the mirror.
Henry Reagan was working on something. But he put on a shield that is used for electric welding and lit up a gas burner. Electric welding is very bright and needs a dark glass. To see something being welded by a gas burner just needs slightly dark glasses. With an electric welding shield he wouldn't have been able to see what he was doing with a gas burner.
During the shootout near the end, Danny is hiding behind Sheetrock which won't stop a bullet (but does and he's standing right where the holes were), and Danny's first two shots make marks in the Sheetrock and his next two make the same marks (with none there prior to the second two shots) and Danny already has blood on his face at the first of the fight scene prior to any blows being placed and before his head is smashed into the mirror which would cause the blood on his face.