"In the middle of the picture both lamps have equal brightness and so each lamp cancels out the shadow cast by the second lamp (unless the feature is big enough so that the lamps create two overlapping shadows). The result is a low contrast area."
Clever explanation, but...why this would only happen at the central region of the image and not along the vertical axis of the photo?
One could argue that in this picture there is in fact a tendency that the off-centrepoint shadows do become deeper when going in the horizontal direction than in the vertical direction. At least I can see no tendency of the opposite effect.
Also: Any offset of the lamp mounts relative to the lens (either in the vertical direction or along the optical axis) would have the effect of introducing off-centrepoint shadows along the vertical axis. This means that the "vanishing shadows" effect weakens along the picture's vertical axis.
Another thing to consider is that according to the spec, the ROV has four searchlights. If all four were lit (assuming they are not mounted on the same horizontal line, and are aimed with converging beams) , the effect would also be that the "vanishing shadows" weakens along the picture's vertical axis.
However, we don't know the specifics of this lighting setup, so this is partly what-if speculation. I'm just trying to point out some possible explanations to what can be observed in the picture.