When you parent a a prop (or anything) to an actor (body part) it parents to the 'origin' (Center Point) of that actor, NOT the surface! The parented eliment will follow the motions of the origin, but changes to the surface will have no effect. You may be able to improve things by the use of ERC, but keeping the rings in the same place on the nipples in all circumstances is probably beyond the practical possibilities of Poser. As long as the nipples stay in the same place relitive to the 'origin' all is fine, but if the nipples move relitive to the origin the rings will stay where thay are.