GitHub repository sandboxes are not fetched

🐛 bug report

Preflight Checklist

• I have read the Contributing Guidelines for this project.
• I agree to follow the Code of Conduct that this project
  adheres to.
• I have searched the issue tracker for an issue that matches the one I want
  to file, without success.

Description of the problem

Hey @sannek / @lbogdan, it seems that certain repositories no longer correctly seem fetched. No information or files can be found:

I think this may be the same issue as happened back in September in https://github.com/codesandbox/codesandbox-client/issues/6109

How has this issue affected you? What are you trying to accomplish?

Examples in our documentation no longer work

To Reproduce

• https://codesandbox.io/s/github/algolia/doc-code-samples/tree/master/React%20InstantSearch/injected-content
• https://codesandbox.io/s/github/algolia/doc-code-samples/tree/master/React+InstantSearch/injected-content

Link to sandbox: https://codesandbox.io/s/github/algolia/doc-code-samples/tree/master/React%20InstantSearch/injected-content

Your Environment

Start by opening the linked CodeSandbox example and reproducing the missing files and information with the two GitHub tree URL variants provided. Check the related issue #6109 for prior context and use the reported Safari and Chrome environments. Done means the documented GitHub repository sandbox loads its files and information correctly.