South Bridge USB part is stroke through by static. Notice that you’d have to test the ground resistance after cutting off power. 
2. There’s USB management module on South Bridge, one manager could take control of two USB interfaces, and namely, South Bridge USB manager has something wrong. USB interfaces are invalid by pair. According to your symptom, we make a conclusion that one manager of South Bridge USB management modules is burnt down, which makes the two USB interfaces there invalid. This doesn’t influence other USB interfaces. Find one line to get other interfaces elicited out. Now, general South Bridges all support more than 10 USB interfaces---if the USB managers of South Bridge are all got stroke by static, then you need to change the South Bridge then.