When trying to download the PortableGit 7z.exe, SourceTree is hit with a 404, because it tries to download "PortableGit-2.51.0-32-bit.7z.exe" for this release: https://github.com/git-for-windows/git/releases/tag/v2.51.0.windows.1

Starting with 2.51, it seems, git-for-windows only deploys 64bit builds of it's Portable Git., making updates impossible with SourceTree 3.4.25

Note: Feel free to adjust severity and priority, but since my install is on a old git version pre-submodule-cve-fixes and the only workaround is to install a system git, I've priorized high.