Cannot modify reviewers after transferring repository to another org

[dduugg]

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Bug

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When transferring a repository to another org, the assigned reviewers to open pull requests with assigned team reviewers become unmodifiable.

To reproduce:

• Create org OrgA, then create repostiory foo and team TeamA within that org
• Create org OrgB, and team TeamB within that org
• Open a pull request in foo, assign TeamA as a reviewer (we use CODEOWNERS to do this automatically, not sure it makes a difference.
• Transfer foo to OrgB

The open PR will still have OrgA/TeamA as the assigned reviewer to the open PR. Any attempt to modify the assigned reviewers has no effect. When attempted via the web UI, there is no visible error, but opening the console shows that the request 404'd (and the list of reviewers is unchanged):

When attempted via the GH API, the following error occurs:

$ curl -L   -X DELETE   -H "Accept: application/vnd.github+json"   -H "Authorization: Bearer $GITHUB_TOKEN"  -H "X-GitHub-Api-Version: 2022-11-28"   https://api.github.com/repos/OrgB/foo/pulls/1/requested_reviewers   -d '{ "reviewers":["dduugg"]}'
{
  "message": "Validation Failed",
  "errors": [
    "Could not add requested reviewers to pull request."
  ],
  "documentation_url": "https://docs.github.com/rest/reference/pulls#remove-requested-reviewers-from-a-pull-request"
}

(This is a bummer, as I'm attempting to fold one org within an enterprise to another, which involves transferring a large number of active repos and associated open pull requests.)

Expected behavior:

The list of assigned reviewers should be modifiable. (The assigned teams from the previous org become invalid on transfer, and this presumably relates to the problem. In our case, we have corresponding team names in both orgs, so a way to update the org component of the team assignment would probably be ideal.)