karg icebear
 

I tried to do the WW pelt trade in, as I've done before, but when I handed it to him I got no item or exp and he did not give the items back. I was waiting for him for a long time so I did it fast and I think I gave him 75pp (ww claw amount) instead of the 100pp for the cloak. He didn't give anything back though if the quest "failed" which I thought it should do. Lag was kinda bad at the time, dunno if that can mess things up.

I tried both the claw quest and the werewolf cloak quest from Karg. Both of them worked fine for me.

As far as turning in the wrong amount of money.. that would most definitely make it fail. Some npcs are scripted to return items, but don't rely on it.