You need to make sure you got the source pinned for UE4.23, so at GitHub click on the link called “releases” and there you will see the sets for each release for UE4 where you can select any unpatched release aswel. Make sure you download the release 4.23, because you if don’t do this and just get the current set at the repository, you will get recently pushed files and it won’t match the release at all.