HerokuにおけるwebpackerのActionView::Template::Errorを直したい(Rails6+docker+webpacker環境)

前提・実現したいこと

dockerで開発しているrailsアプリをHerokuへデプロイしたいのですが、ターミナルでheroku openを叩くと以下のエラーが発生しました。
開発環境では問題なく動作しております
webpackのproductionでの設定に問題がありそうだと予想しているのですが、数日間試行錯誤しており解決に至っておりません。
過去に同様の問題に遭遇した方、解決方法に心当たりのある方いらっしゃいましたら、ご教授よろしくお願いいたします。
足りない情報がありましたら掲載させていただきますのでよろしくお願いします。

発生している問題・エラーメッセージ

heroku logs

2020-05-21T03:49:55.577299+00:00 app[web.1]: [d5c480ba-558b-4df2-bfa4-d6fcdf88dfa6] ActionView::Template::Error (Webpacker can't find application in /docker_dog/public/packs/manifest.json. Possible causes:
2020-05-21T03:49:55.577300+00:00 app[web.1]: 1. You want to set webpacker.yml value of compile to true for your environment
2020-05-21T03:49:55.577300+00:00 app[web.1]: unless you are using the `webpack -w` or the webpack-dev-server.
2020-05-21T03:49:55.577300+00:00 app[web.1]: 2. webpack has not yet re-run to reflect updates.
2020-05-21T03:49:55.577301+00:00 app[web.1]: 3. You have misconfigured Webpacker's config/webpacker.yml file.
2020-05-21T03:49:55.577301+00:00 app[web.1]: 4. Your webpack configuration is not creating a manifest.
2020-05-21T03:49:55.577301+00:00 app[web.1]: Your manifest contains:
2020-05-21T03:49:55.577302+00:00 app[web.1]: {
2020-05-21T03:49:55.577302+00:00 app[web.1]: }
2020-05-21T03:49:55.577302+00:00 app[web.1]: ):
2020-05-21T03:49:55.577303+00:00 app[web.1]: [d5c480ba-558b-4df2-bfa4-d6fcdf88dfa6]      5:     <%= csrf_meta_tags %>
2020-05-21T03:49:55.577303+00:00 app[web.1]: [d5c480ba-558b-4df2-bfa4-d6fcdf88dfa6]      6:     <%= csp_meta_tag %>
2020-05-21T03:49:55.577303+00:00 app[web.1]: [d5c480ba-558b-4df2-bfa4-d6fcdf88dfa6]      7:
2020-05-21T03:49:55.577304+00:00 app[web.1]: [d5c480ba-558b-4df2-bfa4-d6fcdf88dfa6]      8:     <%= javascript_pack_tag 'application', 'data-turbolinks-track': 'reload' %>
2020-05-21T03:49:55.577304+00:00 app[web.1]: [d5c480ba-558b-4df2-bfa4-d6fcdf88dfa6]      9:     <%= stylesheet_pack_tag 'application',  media: 'all', 'data-turbolinks-track': 'reload' %>
2020-05-21T03:49:55.577304+00:00 app[web.1]: [d5c480ba-558b-4df2-bfa4-d6fcdf88dfa6]     10:
2020-05-21T03:49:55.577304+00:00 app[web.1]: [d5c480ba-558b-4df2-bfa4-d6fcdf88dfa6]     11:   </head>
2020-05-21T03:49:55.577305+00:00 app[web.1]: [d5c480ba-558b-4df2-bfa4-d6fcdf88dfa6]
2020-05-21T03:49:55.577305+00:00 app[web.1]: [d5c480ba-558b-4df2-bfa4-d6fcdf88dfa6] app/views/layouts/application.html.erb:8
2020-05-21T03:49:55.577634+00:00 heroku[router]: at=info method=GET path="/" host=shielded-ravine-09485.herokuapp.com request_id=d5c480ba-558b-4df2-bfa4-d6fcdf88dfa6 fwd="106.180.12.82" dyno=web.1 connect=2ms service=19ms status=500 bytes=1891 protocol=https
2020-05-21T03:49:56.280967+00:00 heroku[router]: at=info method=GET path="/favicon.ico" host=shielded-ravine-09485.herokuapp.com request_id=741ce65c-99e9-4395-996c-09795db5f14a fwd="106.180.12.82" dyno=web.1 connect=1ms service=24ms status=200 bytes=207 protocol=https

Railsアプリのコード

docker-compose.yml

version: '3'
services: 
  db:
    image: postgres-data:1.2.1
    container_name: db-container
    volumes:
      - ./tmp/postgres-data:/var/lib/postgresql/data
    environment:
      POSTGRES_USER: postgres
      POSTGRES_PASSWORD: password
      POSTGRES_DB: testdb
    ports:
      - 5433:5432

  web: &app_base
    build: .
    command: >
      bash -c "rm -f tmp/pids/server.pid && 
      bundle exec rails s -p 3000 -b '0.0.0.0'" 
    environment:
      WEBPACKER_DEV_SERVER_HOST: webpack
    volumes:
      - .:/docker_dog
      - /docker_dog/node_modules/
    ports:
      - "3000:3000"
      - "1234:1234"
      - "26162:26162"
    depends_on:
      - db
    stdin_open: true
    tty: true

  pgadmin4:
    image: dpage/pgadmin4:latest
    volumes:
      - ./pgadmin4:/var/lib/pgadmin
    ports:
      - "8000:80"
    environment:
      PGADMIN_DEFAULT_EMAIL: pgadmin4@example.com
      PGADMIN_DEFAULT_PASSWORD: password
    depends_on:
      - db
    restart: always

  webpack:
    <<: *app_base
    command: bash -c "rm -rf /app/public/packs; ./bin/webpack-dev-server"
    ports:
      - 3035:3035
    depends_on:
      - web
    
volumes:
  pgadmin4:

manifest.json

{
  "application.css": "/packs/css/application-6e38df4d.css",
  "application.css.map": "/packs/css/application-6e38df4d.css.map",
  "application.js": "/packs/application-c041cdca59b53f1b1ad7.js",
  "application.js.map": "/packs/application-c041cdca59b53f1b1ad7.js.map",
  "entrypoints": {
    "application": {
      "css": [
        "/packs/css/application-6e38df4d.css"
      ],
      "js": [
        "/packs/application-c041cdca59b53f1b1ad7.js"
      ],
      "css.map": [
        "/packs/css/application-6e38df4d.css.map"
      ],
      "js.map": [
        "/packs/application-c041cdca59b53f1b1ad7.js.map"
      ]
    }
  }
}

webpacker.yml

default: &default
  source_path: app/javascript
  source_entry_path: packs
  public_root_path: public
  public_output_path: packs
  cache_path: tmp/cache/webpacker
  check_yarn_integrity: false
  webpack_compile_output: true

  # Additional paths webpack should lookup modules
  # ['app/assets', 'engine/foo/app/assets']
  resolved_paths: []

  # Reload manifest.json on all requests so we reload latest compiled packs
  cache_manifest: false

  # Extract and emit a css file
  extract_css: true

  static_assets_extensions:
    - .jpg
    - .jpeg
    - .png
    - .gif
    - .tiff
    - .ico
    - .svg
    - .eot
    - .otf
    - .ttf
    - .woff
    - .woff2

  extensions:
    - .mjs
    - .js
    - .sass
    - .scss
    - .css
    - .module.sass
    - .module.scss
    - .module.css
    - .png
    - .svg
    - .gif
    - .jpeg
    - .jpg

development:
  <<: *default
  compile: true

  # Verifies that correct packages and versions are installed by inspecting package.json, yarn.lock, and node_modules
  check_yarn_integrity: false

  # Reference: https://webpack.js.org/configuration/dev-server/
  dev_server:
    https: false
    host: webpack
    port: 3035
    public: localhost:3035
    hmr: true
    # Inline should be set to true if using HMR
    inline: true
    overlay: true
    compress: true
    disable_host_check: true
    use_local_ip: false
    quiet: false
    pretty: false
    headers:
      'Access-Control-Allow-Origin': '*'
    watch_options:
      ignored: '**/node_modules/**'


test:
  <<: *default
  compile: true

  # Compile test packs to a separate directory
  public_output_path: packs-test

production:
  <<: *default

  # Production depends on precompilation of packs prior to booting for performance.
  compile: false

  # Extract and emit a css file
  extract_css: true

  # Cache manifest.json for performance
  cache_manifest: true

config/environment/production.rb

Rails.application.configure do
  
  config.cache_classes = true
  config.eager_load = true
  config.consider_all_requests_local       = false
  config.action_controller.perform_caching = true
  config.public_file_server.enabled = true
  config.assets.compile = true
  config.assets.digest = false
  config.active_storage.service = :local 
  config.force_ssl = true
  config.log_level = :debug
  config.log_tags = [ :request_id ] 
  config.action_mailer.perform_caching = false
  config.i18n.fallbacks = true
  config.active_support.deprecation = :notify
  config.log_formatter = ::Logger::Formatter.new

  if ENV["RAILS_LOG_TO_STDOUT"].present?
    logger           = ActiveSupport::Logger.new(STDOUT)
    logger.formatter = config.log_formatter
    config.logger    = ActiveSupport::TaggedLogging.new(logger)
  end
  
  config.active_record.dump_schema_after_migration = false

  
end

app/javascript/packs/application.js

require("@rails/ujs").start()
require("turbolinks").start()
require("@rails/activestorage").start()
require("channels")
require("jquery")
require("bootstrap")

import "bootstrap-material-design"
import '../stylesheets/application.scss'

import Rails from '@rails/ujs'
Rails.start()

app/javascript/stylesheets/application.scss

@import "~bootstrap-material-design/scss/bootstrap-material-design";

/*
 *= require_self
 *= require_tree .
 */

config/webpack/environment.js

const { environment } = require('@rails/webpacker')

const webpack = require("webpack")

environment.plugins.append("Provide", new webpack.ProvidePlugin({
    $: 'jquery',
    jQuery: 'jquery',
    Popper: ['popper.js', 'default']
}))

module.exports = environment

config/webpack/production.js

process.env.NODE_ENV = process.env.NODE_ENV || 'production'

const environment = require('./environment')

module.exports = environment.toWebpackConfig()

試したこと

ターミナルで以下を実行

$ RAILS_ENV=production bundle exec rails webpacker:compile

production.rbへ以下の追加

config.public_file_server.enabled=true

application.scssへ以下の追加

/*
 *= require_self
 *= require_tree .
 */

environment.jsへ以下の追加

environment.plugins.append("Provide", new webpack.ProvidePlugin({
    $: 'jquery',
    jQuery: 'jquery',
    Popper: ['popper.js', 'default']
}))

application.html.erbから以下の削除（CSSが反映されなくなりました）

<%= javascript_pack_tag 'application', 'data-turbolinks-track': 'reload' %>
<%= stylesheet_pack_tag 'application',  media: 'all', 'data-turbolinks-track': 'reload' %>

webpackerの再インストール

補足情報（FW/ツールのバージョンなど）

ruby '2.7.0'
Rails '6.0.2.2'
yarn '1.22.4'
webpacker '4.2.2'

ディレクトリ構造

-app
 -javascript
  -packs
   -application.js
  -stylesheets
   -application.scss
-config
 -environments
 -webpack
 -webpacker.yml
-public
 -assets
 -packs
  -css
  -js
  -manifest.json