Just started the game in the earliest time period (769?) and about a year in tried to get my King of Kent to marry a Saxon courtier. Couldn't see the button to press to actually seal the marriage. Anyway, clicked on her profile and a few seconds later the game crashed.
Got a "CK2 has stopped working. Windows will notify you if there's a solution to this problem" message.
My guess is you double clicked the double ring icon. From testing today, that spouse selection window is affected by the same bug as the claimants window - if you open or attempt to open one while there is already one open, it'll crash the game eventually because it causes memory corruption once you close it. The crash alternately occurs instantly, in a few seconds, or possibly when resigning the game.
1. open the page of a courtier that can be married [I was testing with betrothals, should be the same]
2. click the double ring icon twice, make sure you hear the noise twice
3. close the spouse window by any method. Clicking another character portrait (which closes the spouse selection window) extremely reliably triggers an instant crash for me, while hitting the x it takes a while to crash - panning the map around etc worked, but it inevitably happened eventually. Hitting the x to close the selection window, it always instantly crashes for me by pressing the rings icon 3x instead of 2x.
As far as I can tell, after step 3 your game is doomed and you're guaranteed to crash sooner or later.
All of this behaves identically to crashes caused by the claimants window, it's just that you can't open a new spouse selection window without closing the old one unless you click the icon multiple times for the same character.
I suspect the realm character list is susceptible to the same or very similar bug, but I haven't been able to reproduce it.
I hope this was clear enough, I'm really tired. tl;dr: the spouse selection window opened by the double ring icon is affected by the "claimant window bug".
