Enter (later renamed Netfabb Studio Basic). It was freeware. It was fast. And it featured the "Extended Repair" button—a magic wand that fixed 95% of broken STLs instantly.
To understand why people hunt for old version installers on GitHub and forum archives, you have to look at the state of 3D printing in 2012–2014. Slicers were primitive. CAD software rarely exported perfect STL files. Models were riddled with non-manifold edges, reversed normals, and holes. netfabb old version
If you manage to find an installer for Netfabb Basic Enter (later renamed Netfabb Studio Basic)