I created a few bugs for stuff in SourceTree that is probably the fault of the 3rd party installer software that you are using and I would like to propose that you replace it with a tiny software that I came to love that is used in many great projects like Visual Studio Code and Atom: Squirrel (https://github.com/Squirrel/Squirrel.Windows) it is open source and should fit the needs of SourceTree quite well.