Sorry, I can't seem to find X Ray mode on CURA, only solid or layers I'm Running version 15.06.03.
From looking at the model in CURA, it looks like its a surface model and not a solid piece of geometry, I suspect it's bad geometry, I guess in future this will just have to be repaired in CAD, I'm assuming CURA isn't able to repair or slice through bad geometry?.
Thanks