Troubleshooting Agent Problems

Problem

A build was failing on the Checkout step:

Git fetch failed with exit code: 1

The detailed log showed the following:

![rejected] CORALv2.3.0 → CORALv2.3.0 (would clobber existing tag)

This was happening after we had followed the procedures to remove a file from our repo's history (see this page). This process updates the hashing algorithms (SHAs) of existing commits.
It seems the build server was unable to perform a fetch of the repository. The best solution in this case was to remove the existing repository from the build server and have it retrieve it from scratch.
To do this we simply had to remove the existing "_work" directory on the build server. On our build server (ncrws494) this lived at the following location: D:\Software\vsts-agent-win-x64-2.149.2.
After doing this we re-queued the build and it worked like a charm.