Several modules were displaying a blue diamond with a character icon and a red exclamation point. I took this to mean that there weren't enough colonists to operate them, even though they were fully staffed (colonist slider set to max). I built a hab module and headed to the station to sell ores and get more colonists. "Warning" icons didn't go away, so I saved and reloaded--icons disappeared and roughly 2K credits/money "fell" into my wallet as well! (I'm guessing they're related somehow.)