How to find the source of the problem of cannot redefine $router

the project is built by vue-cli. SAP, runs without error with npm run dev. After using npm run build, the generated js is put into erb and reported to cannot redefine $router,. Some answers say that vue router is defined twice, or vue is packaged twice, but my analyzer shows that I only packaged vue
analyzervue
I have the following code related to vue and vue-router in the following file
main.js

import Vue from "vue"
import App from "./App"
import store from "./store"
import router from "./router"

import CSRFToken from "./assets/js/csrf-token.js"
import "./assets/css/bootstrap.min.css"
import "./assets/css/style.css"

...

let app = new Vue({ 
  el: "-sharpapp",  
  router,
  store,
    template: "<App/>",
  components: { App },
})

router/index.js

import Vue from "vue"
import VueRouter from "vue-router"
import Index from "@/Index"
import Explore from "@/Explore"
import Question from "@/Question"
import NewQuestion from "@/NewQuestion"
import Notification from "@/Notification"
import Dashboard from "@/Dashboard"
import Dashboard_default from "@/Dashboard_default"
import test from "@/test"

Vue.use(VueRouter)

export default new VueRouter({
...
}

store/index.js

import Vue from "vue"
import Vuex from "vuex"
import router from "../router"

Vue.use(Vuex)

export default new Vuex.Store({
...
})

would you please give us some advice to see what went wrong