Yes, probably the normals. This happens for me usually when i create a symmetrical mesh by copying one half, and then mirroring it. That way the face orientation of the mirrored vertices changes from inside to outside and vice versa. Practically nothing helps. When importing the double defined polygons, poser cannot distinguish which is outside and which one is inside, so it has to guess (and usually it guesses wrong). That leaves essentially two possibilities of what you can do:

Either give the model some thickness, and then, when importing the model, select "make normals consistent" and hope that poser gets this right or,

somehow change the face orientation for the wrong faces in your modeling application (must be counter-clockwise for polygons visible from the outside).

(Note that for the rendering, you do not need to have those double sided polygons, you could simply check "normals forward" in the PoserSurface node).