I have had bizarre things happen with some conforming clothing in Poser, with and without WW. A lot of the old (P4 and P5) clothing provided with Poser has hidden/invisible mesh. Do a conversion, and you have to reset the material to fully transparent. Usually it's called "Skin". It's doesn't need to be there at all. There are other awkwardnesses, but that was the big WTF moment for me.