This happens when the bodies are being pulled together very strongly. Look for control nodes that are well away from their body parts, pulling those body parts towards the other model. Move them back towards their body part.
The way VaM works is thta each control node that is set to "on" is attached to its body part with a virtual spring. When any node is moved too far from its body part, that body part is being pulled toward the node, but held back by the springs attached to other body parts. When the whole body is being held under tension like that, things start to mess up, and it becomes very hard to reposition the model. So rather than just dragging one node farther and farther away, reposition the nodes that are preventing that body part from moving.