Sims 4 Studio Mesh Showing Differently Than Blender's

When I check your mesh in Blender the first thing I notice is this: Faces 3.136 and tris: 4.892. On the outside I can count only 26 visible faces and if you'd like the inside to be also visible then this would be around 50 to 60 faces. Around 400 faces are in the rope grips, which is already much. But this leaves around 2.400 faces unaccounted for. When I try to move faces around, everything seems to be connected to many other things.

To be honest: don't waste your time on this mesh. Something must have gone wrong in the conversion process and now it's a total mess. Sorry to say that but better be honest with you.
The shape is really simple so you should be able to build it in Blender in less than 30 minutes. Keep the rope grips low poly and you'll be fine.

Success!