On Xbox, when selling items to the vendor you get the cash but the item stays on the screen. You have to exit the vendor/merchant or switch to buy back menu then back to sell for the item to disappear..
We are aware and are currently investigating the issue with selling items. With that being said, since there is already a thread opened on this subject, we're going to go ahead and close this one down. To consolidate all feedback, we ask that you continue the discussion here.