websocket error with CRA 4.0.1 and storybook 6

[travis5491811]

Describe the bug
plugin.client.js:85 WebSocket connection to 'ws://localhost:3085/_content/ws' failed: Error during WebSocket handshake: Unexpected response code: 404

To Reproduce
Steps to reproduce the behavior:

1. Install nuxt (with content module option) and nuxt storybook
2. Add a story (can follow the usage from nuxt or directly from storybook)
3. Run storybook with npx nuxt storybook
4. See error in console repeated every second

Expected behavior
No errors

System
Environment Info:

System:
OS: macOS 10.15.7
CPU: (4) x64 Intel(R) Core(TM) i5-8210Y CPU @ 1.60GHz
Binaries:
Node: 14.15.4 - ~/.nvm/versions/node/v14.15.4/bin/node
Yarn: 1.22.10 - ~/.nvm/versions/node/v14.15.4/bin/yarn
npm: 6.14.10 - ~/.nvm/versions/node/v14.15.4/bin/npm
Browsers:
Chrome: 88.0.4324.192
Firefox: 86.0
Safari: 14.0.3
npmPackages:
@storybook/addon-controls: ^6.1.18 => 6.1.18

Additional context
Similar issue reported here

[shilman]

Yee-haw!! I just released https://github.com/storybookjs/storybook/releases/tag/v6.2.0-beta.11 containing PR #14165 that references this issue. Upgrade today to the @next NPM tag to try it out!

npx sb upgrade --prerelease

Closing this issue. Please re-open if you think there's still more to do.