I contacted SS about the black splotches on the left shoulder of my bust. They said they all have them (even their display) and that they are supposed to be shading in the paint but if I wasn't happy with it I could return it for a refund. I still think it looks like someone with dirty hands grabbed the bust but I still love it so I'm not returning it. I tried using a pencil eraser on the spots to remove them but it didn't work. At least mine aren't terribly noticeable since I have it on a high display.
Most of them do have it to some degree. My first one was really bad and had 2 other significant issues. The replacement was a lot nicer and the spots were barely there.