Chris,
I need to mention first that I‘m using the Store version so I‘m not sure how it works at Steam. I assume however that you must have some sort of XBox App or login etc as well? I had the problem of a crashing sim at the last second, too, when the loading bar reached 100%. What eventually helped me was to log out of my XBox account, reboot the PC and log back in. I used the XBox App for that since, obviously, I couldn‘t get to my sim account on the main map.