Hardly the most recent Blender or the Blender Exporter. The version of Blender I downloaded 2 weeks ago was “sub74” and may have changed since then, and the exporter is currently “6.1.1” and I believe @JCPalmer has been making lots of changes to PBR materials over that time
You might want to try the latest editions of everything … and then report results
cheers, gryff 