I tried looking at the source code in the Metahuman plug-in to figure out this error, but alas, there are only binaries in that package from the Marketplace, and the no source code in Epic’s GitHub either. I’m at a loss to figure out how this is supposed to work. It seems this information only exists inside of select few peoples’ brains, yet there are so many people who want an easier way to make custom MetaHumans.