Ok! I have an update!
The issue, after nearly two hours of trial & error, are scorpio-modded weapons, shields and class mods.
Any of those three made with parts of another item or weapon will cause the game to crash upon exit.
I started with a new character and with each save, I added something extra in. It wasn't until I added the stock/impenetrable shields that I noticed the problems. So after removing them, I was able to save/exit my game fine. I then removed them from my level 25 character, and that save file also now saved/exited properly as well.