Storybook stuck loading

Describe the bug In an attempt to update from 6.4.9 to 6.4.14, after building and opening the browser tab, Storybook initially loads into its loading state, but it’s stuck there. It never completes loading its UI, like this:

There are no build errors/warnings, no console errors and no meaningful warnings, and no network errors.

Only thin I can see is /progress which is presumably a part of Storybook, doesn’t finish loading.

I’ve also upgraded @storybook/preset-create-react-app from 3.2.0 to 4.0.0, and in the changelog, all I can see is support for CRA 5, which is all fine - I should assume CRA v4 is not removed, is it? Because that one hadn’t been upgraded. However, downgrading this package back to 3.2.0 works around the problem: Storybook 6.4.14 now loads correctly.

To Reproduce Follow the above description.

System Please paste the results of npx sb@next info here.

  System:
    OS: Windows 10 10.0.19043
    CPU: (12) x64 Intel(R) Core(TM) i9-8950HK CPU @ 2.90GHz
  Binaries:
    Node: 16.13.2 - C:\Program Files\nodejs\node.EXE
    npm: 8.3.2 - C:\Program Files\nodejs\npm.CMD
  Browsers:
    Chrome: 97.0.4692.99
    Edge: Spartan (44.19041.1266.0), Chromium (97.0.1072.62)
  npmPackages:
    @storybook/addon-a11y: 6.4.14 => 6.4.14
    @storybook/addon-actions: 6.4.14 => 6.4.14
    @storybook/addon-controls: 6.4.14 => 6.4.14
    @storybook/addon-docs: 6.4.14 => 6.4.14
    @storybook/addons: 6.4.14 => 6.4.14
    @storybook/preset-create-react-app: ^3.2.0 => 3.2.0
    @storybook/react: 6.4.14 => 6.4.14
    @storybook/theming: 6.4.14 => 6.4.14

(How does this still manage to miss the one browser I’m actually using??)

Additional context Other packages noteworthy:

• Craco 6.2.0 - using Craco means we have no direct control over whichever CRA version it uses.
• Webpack 4.46.0 - Updating to 5.x gave us a myriad of weird problems, so we decided to stick with v4, which should be fine because that one isn’t EOL yet.

I’m in the process of updating (or trying to, honestly) our dependencies to their latest, and I would like small chunks of updates at a time. Updating too many packages in one go makes it difficult to diagnose problems. So yeah, I could also update Craco, but I don’t want to just yet, because it’s not only Storybook depending on it.