Progress saving isn't working in Career mode

I'm playing on Linux Mint with Proton compatibility on Steam, so maybe that's the problem, but I've noticed that any progress I make in career mode, including building ships and records, doesn't survive between my computer turning off and on again. Strangely enough, progress is kept if I just exit the game and return later, but not if I turn off the computer.
Progress in Creative mode seems to work. At least ships built or modified there are still available.