Help with gh-pages

Hello,
could you help me with a problem? My students must fork a repo, make some changes, and finally create a gh-page. The first days,it was ok but the last days, they receive the following message:

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The page build failed for the gh-pages branch with the following error:
A file was included in _biography/[alan-kay.md/#excerpt](http://alan-kay.md/#excerpt) that is a symlink or does not exist in your _includes directory. For more information, see https://help.github.com/en/articles/page-build-failed-file-is-a-symlink.

Blockquote

The file is included in the directory but the page cannot be build. Do you have any suggestion what the problem is
Thank you in advance

Did you do this via git or manually?

Thank you! They commited changes to a yaml file through github. In the beginning, they could see the changes on the gh-page and then they couldn’t. I am wondering if this could be solved without using git.