So a few days ago, my cousin in Vietnam complained to me about how slow his internet is. He said his dad was doing something to the router and his speed suddenly drops to around 0.4Mbps after he moved like 10cm away from the router. I asked him if his dad used a wifi jammer but he said no. He can't even watch Youtube or play PUBG with me since his speed dropped so bad . Does anyone know what caused this ? Thanks for reading this.