You need to be careful as to which model you are changing textures in this manner. IIRC, Miki4 only has one texture map, some of the earlier DAZ models might have one texture map. But Vicky3/4 has two texture maps, one for the face and the other for the rest of the body which includes the back of the head. Once you've established an acceptable arrangement of shader nodes for your character, create a material collection so you can reapply the texture correctly. If you have Poser 11 Pro, you can also create a MATPose file.