You're totally right, big thanks for your feedback. Until we'll release a public update (might be, we'll tweak some materials slightly until than), please feel free to use attached Corona's material library with corrected links to Translucency maps and removed duplicated materials.
All bundled material libraries are stored by default at
C:\Program Files (x86)\Itoo Software\Forest Pack Pro\matlib
in several files corresponding to used renderer (3d_vray.mat, 3d_thea.mat, 3d_standard.mat, 3d_octane.mat, 3d_mental.mat, 3d_corona.mat). To apply this patch, please overwrite your local copy of 3d_corona.mat with attached one.
If you have any suggestion(s), that may improve these materials, please feel free to let us know.