Skeletal mesh is not visible in mobile preview after updating to UE4.21

Spoke too soon - the FBX export → import in 4.21 loses UV coords so textures look grey for some characters from Synty PolygonWesternFrontier, and I have no idea why. Any ideas? SK_Chr_Hunter_Male_01 works. SK_Chr_Salesman_Male_01 on the other hand is all grey because UV’s appear to have not come across in the process.