Beyblade 3D model problem

Hey guys!

I've designed a beyblade plastic gen attack ring years ago, the printed version was meant to be a birthday present from my friends.
Unfortunetaly the model had some issues and couldn't be uploaded to a printing service.

 I'm not that much into 3D modelling to fix these problems myself... We have access to a printer and it accepted the model, but only two objects were fully printed, the rest of the attack ring was hollowed and had no shell (even though it was enabled). So there are still problems with the model. I've tried to fix it with Autodesk Netfabb, but now the printer won't accept the model at all.

I'm a bit lost tbh... I've attached the STL file, maybe someone has a bit more insight in the whole 3D printing stuff and can help me out in any way :)

Link (STL file)