Originally Posted by
QuintusSertorius
Usually because that particular region qualifies twice for some reason or another. Does the building in question use region_religion or particular hidden_resources to determine where it can be constructed? If it satisfied a condition more than once, it appears more than once. Furthermore, alternative upgrade paths aren't parsed as "or", so again if it qualifies for more than one of the upgrade options, it'll display them all.
Post the building (wrapped in [code] tags) and we might be able to see what's happening.