this problem is actually common when trying to work with poser exports. sometimes the file doesnt create enough data for the normals to translate it. I always found the best fix is to export the model only in another format like .dxf and reimport it. or try manually assigning normal directions.
And after calming me down with some orange slices and some fetal spooning,
E.T. revealed to me his singular purpose.
--TOOL, 10,000 Days---