What is the problem:
The weekly earnings (or loses) aren't added to my money total. Only the money gained from selling my shares has an impact.

What I've tried:

• I've tried different start-ups (the tutorial one, the weather predicting one, self-driving car, tracking systems, and tatari).
  
• I've tried different saves (both existing (previously working) and new ones) without it having an impact.
  
• I've tried completing "normal" missions, those earnings are processed as normal.
  
• I've tried restarting the game several times.
  
• I’ve used Steam’s “checking integrity”-feature (if that’s what it’s called in English).
  
• I’ve reinstalled the game.
  
• I’ve restarted my PC.

What I think the trigger was:
I'm not 100% sure, but I think that this problem first appeared after I paid back a loan (I paid it before it was due). After that I definitely had trouble earning money, which is why I started a new save. I can't say for sure that it only affected start-ups at that point (but right now that save behaves like all others do).
The new save used the checkpoint “RNN” (from which on I played missions until I could do the weather predicting start-up). I then did the tutorial start-up, but I can't say if it behaved normally because I didn't care about it. I then did the weather-predicting one (just in case it matters: I first connected some nodes and clicked "release" before I was ready. I therefore patched it before its first day generating money). After one ingame week I definitely didn't earn the money from that start-up that I was due.

Now, is there any way to fix this? Because I really want to earn that cat-o-holic-achievement, but right now I can't do that, seeing as not only the existing, but also all future saves are corrupted. I’m willing to manually manipulate files if necessary (even, if that should help for some obscure reason, hexdumps).

Oh, and should it be relevant: I'm playing on Windows 10 and am not using Cloud-save.