I wish I could be more help but since I don't have ZBrush I can't try it myself. Do you have any other apps that can manipulate geometry? I was just thinking you could try making a morph with something else, even if it's just a garbage morph, just to test the process. That might tell you if it's a ZBrush problem or something else. I'm glad you like her knees and elbows. We spent a lot of time on those.