I noticed this some time ago and thought it might come up here, but haven't seen any specific references to it.
I'm seeing problems with displacement (bump) mapping on imported objects in recent frontier releases of Terragen. Version 4.4.45 (which I think is the most recent official release) works fine. But with later frontier versions bumps along edges, and negative bumps, seem to create ridges that cast shadows and render much darker than the rest of the object.
Has anyone else noticed this?
(Forgive the low-quality noisy renders.)
Edit to note that the rope displacement is slightly negative, all other displacements are positive.