If you link me a copy of the model, I'll prep it for Poser. What I'll do: import it into Wings3D, set all edges to hard, add a level of Subdivision; which will increase the poly count and convert to quads without distorting the shapes, set edges back to soft and export back out as obj. Hopefully UVs won't be too distorted, probably not, which might be moot anyway. I'll also weld identical if necessary. I'll link back the new OBJ to here. Just add 1 level of Subdivision when obj is back in Poser.

It should take about 15 minutes total.

If not, at least you have a sort of roadmap for how to fix it.