The sphere is incorrectly assembled, so the openings do not match up. The chair and rail assembly for the cosmonaut was also not inserted prior to the sphere being closed, so it was impossible to get it in. Will have to disassemble.
The inside of the 3rd stage didn't look nice, so I covered it with a sheet of 0.4mm styrene. I will have to think about adding some details later to make it more interesting.