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If your talking about that zigzag line across the butt, I don't think its a subdivision or smoothing error. It looks like a split edge, along a material zone (or perhaps just a phong break, I can't tell.) The smoothness of the rest of the mesh suggests theres no problem with smoothing or sub-division.

Is there a split/break on textures option either in the export or in the import that needs switching off?

Actually, it's one of her fingers poking through her backside.

 

Oh wait no ... you're talkng about what looks like the seam between the hip and the waist, or more probably the hip and the thighs or buttocks. That is possibly where the two groups meet.