As you see crashes have not gone completely though they are much fewer than before. To be fare with CA hardware is sometimes responsible for random crashes, due to RAM problems. Also if there are many saved_games in your game save folder, it is a reason for (rare) random crashes. Another rare crash is some fleet stuck with another somewhere on the global map (especially in narrow straights).
Now in your case, crashing on Prussia does not mean that the problem is with Prussia, it could be with any other faction that Prussia is in contact. If you are interesting to find a clue about it you can make last auto_saved_game a startpos.esf file, start the campaign as Prussia and check it. You can find
here a how to make hybrid startpos. If you proceed to that don't forget to Keep a buck up of your startpos first.