Cape Cod Glass Final

"Cape Cod" Cordial Glasses, with Decanter and Plate. 

I'm really happy with how these look in Blender, but in Painter and UE, turning on opacity really messes things up. Parts of the mesh go altogether invisible while the rest is weirdly see through. 

I don't know enough about the other two programs to know if it's me or my mesh. 

Of course, I'd like to say that my mesh is clean. I checked it up and down. My normals are pointing proper, the UV map is clean with no overlapping faces, I've checked for double or loose geometry, it all seems to be as it should be. I know that could still be the case though, if nothing else. I'm still pretty new at this. 

If you have any ideas as to what might help, please reach out!