i've found that they seem to spawn 1 every now and then loosely based on a 'time cycle' so as you explore it places one in the loaded area of your player; also network connectivity to your PC/laptop may be a factor.
Here is my complete seabase at the point of rocket launch(i took the main menu screenshot when the gun was disabled and rocket was ready to launch): in SeaBase ShowcaseComment by The_CreamsterMarch 2018
As these 'ejectable' modules are located in the room with the starship Blackbox Recorder Terminal the logical thing is they would be "modular, replaceable system critical hardware(could be all-in-one system hardware modules; CPU, RAM, Storage)"
I haven't experienced quite that yet, but around 2hrs after my previous save of my 2nd playthrough in freedom mode(had mostly done base building stuff so not too much of a worry) it simply refused to save and the game process was still running as i …