I dug a little deeper. If you want to get hacky, you could go into:
C:\Users\[your username]\AppData\LocalLow\Schell Games\Mission - It's Complicated
...and edit the globalgameState.json file.
What's the "_resolutionIndex" value you're seeing? 7? If it's not 7, try 7! If there's a section that says "_fullscreen": true, try deleting it to get you in windowed mode. Maybe that'll behave better?
Anyway, this is all goofy and not a real fix, but idk maybe you're dying to play? If you don't feel like messing with this I understand, hopefully we can get a fix in soon!