Unreal Inventory System Course - #10 Chests 

probably the easiest fix there yeah, could maybe also check if the inde of the slot you're trying to merge with is the same as the index of the slot you room the items from, if it is, just cancel drag drop operation but that's pretyt much what you seem to be doing too. I personally ended up replacing the drag and drop system with a much less bug prone click system (like most games actually have) oon the parteon exclusive bonus episode. but to give you a general rundown of how that works, whenever you click, instead of starting a drag drop oppertation, it spawns in a new widget that hold jsut 1 item slot and that widget follows your mouse around on even ttick, when you clcik on a slot, the system checks if this widget exists, if it does, it places that "hoverslot" into whatever you clicked on, and if no " hover slot" exists yet, it takes the slot you just clicked on , makes a "hover slot" from it and empties the original slot. so with that, you don't get bugs surrounding being able to remove or potentially duplicate items because they don't exist in 2 places at once like they do in the systems used in the tutorial series :)