Someone continuously buying and returning the same item – Scam?

Is this some sort of scam? I’ve had the same person buying a large quantity of one of my items, one at a time, over a month or so, then a few weeks later, claiming refund for ‘shipping not received’.

I tried contacting Amazon about this and they said they won’t investigate until after 60 days. Meanwhile, my inventory is depleting from this activity.

Is there anything I can do?