Hello Nick,
In order to achieve what you want you should enable the "Do not delete extracted MSI and CAB files" option from "Builds -> Configuration ->
Bootstrapper Options" group.
Please keep in mind that when Windows Installer installs an MSI file it caches it in the hidden
Windows Installer Cache directory . Also, the cached MSI is stripped of any files it may contain for saving a significant amount of space required by large packages. This is part of the reason for prompting for source when the original media files aren't available.
When run a repair, if the required MSI and media files are not available Windows Installer will search for them in the original location the MSI was originally installed from. If they aren't located then will prompt for it.
Also, you can take a look on our
"Repair failures" thread.
All the best,
Daniel