I'm not much help, as I haven't laid my hands on the paper yet, but it sounds like the same problem the scanner has with glossier canvas. The specular highlights from the reflection off of the canvas freak out the scanner. Is there enough texture with the Harman gloss that this might be the source of the problem? I think smooth glossy surfaces and less glossy textured surfaces are less of a challenge. I thought that this paper was extremely smooth, however, so it may be a different problem entirely.
-Ron H.
PS: What was your experience with linear transport marks on the profile patches?