I played around with it a bit and it is related to the Realtime Reflections setting. If it is on, the dragoness skin causes weird rendering in the inner thigh area. This can be fixed for now by turning that setting off or by enabling the Translucenc…
I've seen this happen as well. It really only happens on the very top inner part of the thighs. It seems to be a bit of a rendering glitch and I don't know if it is related to the translucency shader. Haven't actually tested it out yet.
I think a better approach would be to have a "Force" prop that you could attach bones to. You could define whether it's radial or linear and than other properties for speed and possibly oscillation.