Is it all dynamic or is there a  transition from dynamic to fixed (through Surface settings or a weight map) in thata rea? You may be able to test by simualting the outfit on its own, no wearer.

Another issue, though it shouldn't lead to the lumpiness seen here, is that clothing is often modelled fairly loose on the figure, so when it is simulatedall that looseness allows everything to drop more than a physical garment would.