Bad slicing results of model

[acc15]

Model:
https://www.thingiverse.com/thing:1388237

Problems is
* Simplify3d tries to print on air.
* Bottom of model printed partially filled however model contains holes.
* Whole slicing result looks very fragile (and i actually print it - it actually fragile)
* Poor sliciing performance (100% CPU usage on 4.2GHz 16threads)

Simplify reports that model is manifold and slices bad.
Repetier reports that model is non-manifold and slices good.
...

Maybe i miss some settings?
Whats the problem with this model?

Slicing results of Simplify vs RepetierHost (Cura) in attachments