winnerwinner

Item : Any item you try to sell to NPC vendor. Date tested : March 30, 2014 How it works : You can only sell one item to the vendor at a time. How it should work : You can sell any number of items to the vendor at once. Realm : 5.4.2 100x

If you try to sell items to an NPC vendor, it will grey the item out but not sell it, making you unable to vendor items. I noticed that it only happens if you are selling several items, it rarely occurs if you sell just one.