I don't know if this is a bug from earlier versions 6. 3 being the 1st that I have played.
But when I started a conventional empire with missile bases all the 'crew' on them started dying from exposure.
This kept going untill everybody in them was dead
It feels like the older bug introduced when the life support changes were first implemented, a persistent little heisenbug that's resisted every effort at solution. In the present version, can be fixed in the same way: Delete the offending PDCs generated at game start, replace them with a new set of PDCs in SM Mode.
Oh, and on a related note, I couldn't use the "SM Add" button to generate installations or PDCs in the Industry screen for some reason, even with SM mode activated. It still appears to activate in SM mode for Missiles, Fighters, and Ship Components, but not for Installations or Build PDC / Orbital Habitat. To fix the above, I had to use the Fast OB menu option. I'm not sure if this is a bug or intended design feature, though; I haven't often had occasion to manipulate installations in SM mode before.