The appearance of Godzilla's face changes throughout the film, primarily in closeup shots. This is because a mechanical Godzilla puppet head is used in many closeup shots and does not completely match the Godzilla suit's head design.
In one shot, the infamous giant Godzilla foot is used and the top border of the prop can clearly be seen.
When Godzilla is first seen on-screen, the camera pans up to reveal his face. The soldier who first sees Godzilla is poorly composited in this panning shot, as the panning between two do not match up with each other.