It seems to have something to do with self collision. Maybe it tries to collide with itself and the figure underneath. I was facing this problem when I played around with making a multilayered skirt. I couldn't get the collisions to work properly with self collision. The band of a skirt underneath would poke through the top skirt (soft decorated), the bottom skirts would also poke through as a dynamic group. I tried high density models both as quards and triangles and the same problem would arise (sometimes in different manners, but it persisted)