I was finally able to build shops in my settlements but noticed an issue. I built 4 shops and on the 4th shop I think it's the weapons one, when I assign a person to that particular shop they don't ever go to it and stand there. They just continue to stand where they're at originally. When I go up and talk to that person they give you options like they are at the booth selling guns. This is the same at both of my settlements. Not sure if anybody has experienced the same thing.