Screwed-up 3D model from Thingsverse?

I downloaded a Makita router dust shoe from https://www.thingiverse.com/thing:2743339
When I checked the model in Simplify3D, it reported errors. I tried to fix the model in 3D Studio MAX, Inventor, and MeshMixer but I couldn't do it. Can someone try to fix this model for me?

I dumped the model into Meshmixer and it effectively destroyed most of the walls. When S3D took it in hand, it appears that the "castle walls" are incorrectly joined and there's a section of the castle that floats with a large gap, at just about wall-top level.

it would have been useful if the creator provided his source files. I'm not qualified to perform a fix, as I suspect it would be best done in Fusion 360 or Blender, very different programs to each other.

Like this. I used ideal-Maker to repair 62 Non-Manifold Edges.
Cura 15.04.6 and NetFabb Studio Basic appears to load the STL correctly as is.

Raise 3D ideaMaker 3.1.7 download

Works perfectly in Solidworks and Geomagic Design for me, I can try in Blender later if you need.

I wonder if a lot of these weird issues are down to the type of stl file ?

There are 2 types that I know of: binary and ascii.
had a problem importing an stl file into openscad yesterday. Loaded into simplify3d and saved as binary stl and it loaded fine into openscad after that. Presumably the original was ascii.

Does seem odd that different programs can 'see' stl files quite differently.

Thanks for sharing!