I think you're on the right track. I have noted that when the maps are universal (one map to rule them all), sometimes something slips through. Or the way the artist set them up was not the look I was going for. Geometry/cutout opacity maps are famous, as are translucency and specular. There have been times where the only option was to discard the map for a particular section and trial and error it manually, or substitute a different map.