I saved after I started my rocket and reloaded the game. Now all the rocket modules exept the command module are missing: 1x steam engine, 3x research module.
In the attached save file you can see the rocket will return without the modules. Gossmann will be kicked out of the rocket when the landing is complete.
Save file before launching: Planet 73 SU-Update.sav
Save file before landing: Planet 74.sav
Start a rocket, do a save and reload and wait for the rocket to return. Or just load my save file "Planet 74.sav".