This happened when I tried to increase Collin's songwriting stat. When the bar indicating how close you are to finishing a song filled up, I got an error. I'm not sure if it'll be helpful, but I can send the traceback text if needed. When I rollback, the game closes.
Although I wasn't linked to any traceback files on Wizz's route, it was strange that even though I had already broken up with Beau, the scene where he finishes his studies and gets Robin to sort-of-move-in still plays as if Robin and Beau are in a romantic relationship. However, when I went on Wizz's route for the second time in another playthrough (also choosing Beau as my previous love interest), everything worked just fine.
Thank you for creating this amazing game! :)