I entered two local photo contests which had very similar categories, and entered the exact same photos.
In one contest, I won first place in two categories, and got honorable mention in another three. I also won best of show.
In the second competition, I won first in one category (different than the above first place winners) and honorable mention. The two first place winners from the previous competition didn't even get honorable mention.
Judges are strange, and photography is subjective...which makes the outcome of most competitions very random.