Found a pretty serious bug that causes profile corruption. It seems that if you try to sell an item that it for some reason can't find a price for, it returns NaN for the price and corrupts the "money spent" for the blackmarket trader. This immediately causes everything to freeze, and if you restart you are greeted by a screen that tells you that there was an error loading your profile.
This is what the console outputted when I tried to sell Big Pipe's pipe: "Blackmarket: sold item_equipment_mustache NaN"
This is what the screen showed for the error:
I was able to fix my profile by editing my profile JSON manually and changing the salesSum value from "null" to 0.