Fail to fork the very repo for HTTP 500 error

[SihanLu212]

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Hi there,

I'm new to GitHub API and found that I can't fork some repo via API v3, but I can manually fork it. But for other repos, both are okay.

e.g.

https://github.com/dgiot/dgiot

For the https://github.com/dgiot/dgiot , the API always returns 500 error.