Hi
The update process can occasionally stall if there is a process running, e.g. Git Credential Manager or openssh, from inside the the git folders or if the process was installed as admin at any time.
Ultimately, closing Sourcetree and manually deleting the %localappdata%/Atlassian/Sourcetree/git_local folder and restarting Sourcetree will trigger an optional re-install of the bundled git.
Thanks minnsey!
Resolved the issue by: