vue-cli-service serve and buid generating different styles

I'm not sure how to show it but for some reason after vue-cli-service build and vue-cli-service serve page looks different. In the case of build all is fine but in the case of serve styles are messed, but there are no errors while building and no error in the browser console. I can share the package.json if it can help and some other configuration files I have...

package.json

{
  "name": "newlanding",
  "version": "0.1.0",
  "private": true,
  "scripts": {
    "serve": "vue-cli-service serve",
    "build": "vue-cli-service build",
    "lint": "vue-cli-service lint"
  },
  "dependencies": {
    "core-js": "^3.6.5",
    "vue": "^2.6.11",
    "vuelidate": "^0.7.5",
    "vuetify": "^2.2.11"
  },
  "devDependencies": {
    "@mdi/js": "^5.4.55",
    "@vue/cli-plugin-babel": "~4.4.0",
    "@vue/cli-plugin-eslint": "~4.4.0",
    "@vue/cli-service": "~4.4.0",
    "babel-eslint": "^10.1.0",
    "eslint": "^6.7.2",
    "eslint-plugin-vue": "^6.2.2",
    "sass": "^1.19.0",
    "sass-loader": "^8.0.0",
    "vue-cli-plugin-vuetify": "~2.0.7",
    "vue-template-compiler": "^2.6.11",
    "vuetify-loader": "^1.3.0"
  },
  "eslintConfig": {
    "root": true,
    "env": {
      "node": true
    },
    "extends": [
      "plugin:vue/essential",
      "eslint:recommended"
    ],
    "parserOptions": {
      "parser": "babel-eslint"
    },
    "rules": {}
  },
  "browserslist": [
    "> 1%",
    "last 2 versions",
    "not dead"
  ]
}

vue.config.js

module.exports = {
  "transpileDependencies": [
    "vuetify"
  ]
}

babel.config.js

module.exports = {
  presets: [
    '@vue/cli-plugin-babel/preset'
  ]
}

I know it's hard to find the reason without the actuall code... but maybe you have some suggestion, I do not know where else to look, as I told before no errors while building and in browser, also no errors in yarn-error.log.