Customer claims they have received an empty box?

This is something we have experienced many times both with Seller and Vendor accounts. We sell jewellery.
It can be the customer trying to get a free item, courier theft or theft within the warehouse.
From my experience (I’ve been selling since 2006), 90% of the time the items “go missing” in the warehouses.
Over the years we have had regular spates of jewellery going missing… Amazon were sending out empty boxes to customers. Our account managers have even admitted it is an issue.
We have limited this to some extent by making the jewellery boxes more difficult to open. Previously, each jewellery box was in an open ended sleeve, meaning you could slip off the sleeve, open the box and the jewellery could drop out. If you were deft, you could do this within a couple of seconds, allowing the jewellery to fall into your boot or bag maybe. Now, each jewellery box has another outer cardboard box that is sealed with tape. If you try to open it, you will damage the outer sleeve.
The upside is that the occurence of missing jewellery has greatly decreased. The downside is that genuine customer returns get sent back as unfulfillable innventory instead of going back into FBA stock.
For each empty box issue we will raise a claim. It’s very hit and miss whether Amazon will refund us for the missing item.
It is important to raise a claim and report EVERY missing item, because Amazon need to be made aware that there is potentially an issue in their warehouses with stock security.
Basically, although we are not happy about it because it means the customer doesn’t trust our brand and we worry about the security of our high value stock, we accept that it’s collateral damage and only a tiny percentage of the large quantity of product we sell through Amazon.