If you close an issue or pull request via a commit message on GitHub (see GitHub linking issues for a full list of messages supported), the link created used at the "Changes" tab invalid.
It uses the following pattern: https://github.com/<org|user>/<repo>/issues/<issue id>/find
The appended /find is out of place and will lead to a 404 on GitHub, removing it makes the link valid again.
I attached a screenshot, clicking on "Closes #..." will lead to the invalid URL described above. Making it valid requires removing the /find at the end.