title: Getting "throw new Error('Callback was already called.')"
body: <p>I've been getting this bizarre error out of the blue when I run npm run build (built the program many times before).</p>
  <pre><code>C:\Users\PomoJota\node_modules\neo-async\async.js:16
      throw new Error('Callback was already called.');
      ^
  
  Error: Callback was already called.
      at throwError (C:\Users\PomoJota\node_modules\neo-async\async.js:16:11)
      at C:\Users\PomoJota\node_modules\neo-async\async.js:2818:7
      at processTicksAndRejections (node:internal/process/task_queues:75:11)
  npm ERR! code 1
  npm ERR! path C:\Users\pomojota
  npm ERR! command failed
  npm ERR! command C:\Windows\system32\cmd.exe /d /s /c vue-cli-service build
  
  npm ERR! A complete log of this run can be found in:
  npm ERR!     C:\Users\Jean\AppData\Local\npm-cache\_logs\2021-07-27T03_46_08_599Z-debug.log
  </code></pre>
  <p>The debug log:</p>
  <pre><code>0 verbose cli [
  0 verbose cli   'C:\\Program Files\\nodejs\\node.exe',
  0 verbose cli   'C:\\Program Files\\nodejs\\node_modules\\npm\\bin\\npm-cli.js',
  0 verbose cli   'run',
  0 verbose cli   'build'
  0 verbose cli ]
  1 info using npm@7.3.0
  2 info using node@v15.5.1
  3 timing config:load:defaults Completed in 4ms
  4 timing config:load:file:C:\Program Files\nodejs\node_modules\npm\npmrc Completed in 3ms
  5 timing config:load:builtin Completed in 3ms
  6 timing config:load:cli Completed in 2ms
  7 timing config:load:env Completed in 1ms
  8 timing config:load:file:C:\Users\pomojota\.npmrc Completed in 8ms
  9 timing config:load:project Completed in 10ms
  10 timing config:load:file:C:\Users\Jean\.npmrc Completed in 4ms
  11 timing config:load:user Completed in 4ms
  12 timing config:load:file:C:\Users\Jean\AppData\Roaming\npm\etc\npmrc Completed in 1ms
  13 timing config:load:global Completed in 1ms
  14 timing config:load:cafile Completed in 0ms
  15 timing config:load:validate Completed in 0ms
  16 timing config:load:setUserAgent Completed in 1ms
  17 timing config:load:setEnvs Completed in 1ms
  18 timing config:load Completed in 29ms
  19 verbose npm-session b0696214e645b814
  20 timing npm:load Completed in 53ms
  21 timing command:run-script Completed in 8397ms
  22 verbose stack Error: command failed
  22 verbose stack     at ChildProcess.&lt;anonymous&gt; (C:\Program Files\nodejs\node_modules\npm\node_modules\@npmcli\promise-spawn\index.js:64:27)
  22 verbose stack     at ChildProcess.emit (node:events:376:20)
  22 verbose stack     at maybeClose (node:internal/child_process:1063:16)
  22 verbose stack     at Process.ChildProcess._handle.onexit (node:internal/child_process:295:5)
  23 verbose pkgid pomojota@0.1.0
  24 verbose cwd C:\Users\pomojota
  25 verbose Windows_NT 10.0.19042
  26 verbose argv &quot;C:\\Program Files\\nodejs\\node.exe&quot; &quot;C:\\Program Files\\nodejs\\node_modules\\npm\\bin\\npm-cli.js&quot; &quot;run&quot; &quot;build&quot;
  27 verbose node v15.5.1
  28 verbose npm  v7.3.0
  29 error code 1
  30 error path C:\Users\pomojota
  31 error command failed
  32 error command C:\Windows\system32\cmd.exe /d /s /c vue-cli-service build
  33 verbose exit 1
  </code></pre>
  <p>My package.json:</p>
  <pre><code>{
    &quot;name&quot;: &quot;pomojota&quot;,
    &quot;version&quot;: &quot;0.1.0&quot;,
    &quot;private&quot;: true,
    &quot;scripts&quot;: {
      &quot;serve&quot;: &quot;vue-cli-service serve&quot;,
      &quot;build&quot;: &quot;vue-cli-service build&quot;,
      &quot;lint&quot;: &quot;vue-cli-service lint&quot;,
      &quot;deploy&quot;: &quot;sh deploy.sh&quot;
    },
    &quot;dependencies&quot;: {
      &quot;core-js&quot;: &quot;^3.6.5&quot;,
      &quot;vue&quot;: &quot;^3.0.0&quot;
    },
    &quot;devDependencies&quot;: {
      &quot;@vue/cli-plugin-babel&quot;: &quot;~4.5.0&quot;,
      &quot;@vue/cli-plugin-eslint&quot;: &quot;~4.5.0&quot;,
      &quot;@vue/cli-service&quot;: &quot;~4.5.0&quot;,
      &quot;@vue/compiler-sfc&quot;: &quot;^3.0.0&quot;,
      &quot;babel-eslint&quot;: &quot;^10.1.0&quot;,
      &quot;eslint&quot;: &quot;^6.7.2&quot;,
      &quot;eslint-plugin-vue&quot;: &quot;^7.0.0&quot;
    },
    &quot;eslintConfig&quot;: {
      &quot;root&quot;: true,
      &quot;env&quot;: {
        &quot;node&quot;: true
      },
      &quot;extends&quot;: [
        &quot;plugin:vue/vue3-essential&quot;,
        &quot;eslint:recommended&quot;
      ],
      &quot;parserOptions&quot;: {
        &quot;parser&quot;: &quot;babel-eslint&quot;
      },
      &quot;rules&quot;: {}
    },
    &quot;browserslist&quot;: [
      &quot;&gt; 1%&quot;,
      &quot;last 2 versions&quot;,
      &quot;not dead&quot;
    ]
  }
  
  </code></pre>
  <p>I am utterly lost, don't even know where to start on this.
  For reference I followed this guide to deploy a vue.js app to github pages: <a href="https://www.youtube.com/watch?v=i_XbW-FsLKk" rel="nofollow noreferrer">https://www.youtube.com/watch?v=i_XbW-FsLKk</a> and it has been working fine up until today when I got this error out of the blue.</p>