When builds are recycled, their source field is not updated. This was originally reported by @churchyard as fedora-infrastructure ticket 7408.

For example Fedora build python3-3.7.1-4.fc30 has source pointing to commit 31d9637 while in fact the build was done from a different source - commit 4f22584. This happened because the build was first attempted from commit 31d9637, but it failed. Then a new build task was submitted from commit 4f22584, leading to the previous build being recycled. However source was not updated.