Yeah… we’d need a lot more of te code to go over it but nobody is likely to be down for understanding youur whole inventory class to help you out so you’re likely largely on your own.
I recommend you try something like the rubber ducky method, explain your code step by step in detail to a rubber ducky, node by node.
The concept of what you do is simple enough yeah? You have a structure for inventory content, item name and amount is what you’re using, i’d probably do it different myself but to each their own with those details.
Then you have a container with a set number of slots, and you put the structure in that slot.
Then when you click and drag it, you hide the icon and display a duplicate of it next to the cursor.
Then when you release the mouse button if you are over a valid slot, the structure is moved from it’s original slot to the new lost, but if you are not over a valid slot, the icon is removed from the cursor and unhidden for it’s original slot.
Now I have no way to tell how you’re trying to do that because your blueprint screenshots are tiny (zoom in man!), but something is clearly going wrong with the movement process for you. Namely the removal part.
Now my first guess is that the branch in your second image is going to false instead of true failing the duplication and leading to the duplication bug.