This is looking good. I agree about the skirt settling for a bit longer - if you haven't already, try setting the final pose at an earlier stage in the simulation. You may not need extra frames, even. I have that same trouble with constrained vertices. I'm not positive, but I think it happens when the collision offset and/or depth are incompatible with the starting position of the cloth. The constraint fights the collision depth setting in some way. Try adding the placket to the soft decorated group. If you give it a separate material zone, that will make it easier to select.