heyas, think Jim gave us a good hint. Yes indeed, this part which can be seen transparent in our image, was duplicated in RDS and turn around with 180. There are no normals (vn) imported into Poser. Nevertheless we got the solution how to erase this transparency in Poser. It's just a blemish, because after we have rendered the model, it is shown correct. First we thought, uv-mapper can fix this problem, but is doesn't.