Also there have been a few threads recently on the forums about a certain buyer who likes to claim INR or INAD and then swaps out the item for an old non working item.

Look at the thread called User in seller central

These posts have multiple sellers who have had this happen to them by the same buyer

If you google this buyer you can see it has been happening for well over a year.

How Many cases can one buyer open and keep getting away with it?