So I was practicing the route on PS4 today and had this happen. This happens every instance when you try to sell items, even after reloading and continuing on in the game this still happens. The only solution is to exit out of selling items after 3-4 items and re-enter, and double-check the item you want to sell is actually the one being sold.

For some reason the game seems to move items around after you sell them but it bugs out? I'm not even sure what exactly is happening.