Hello. As I said many times before, it is not my addon's side issue. I'm almost sure your problem is that model of ragdoll you try to "NPCify" does not support NPC class you selected. Solution is to somehow get name of NPC class ragdoll came from, and set it using console command. There is no known automatic fix. If ragdolls stored information about what NPC it was before, it would be easier.
Edit: I added tool to get class name easier. Check out description or change log.