Strange Pattern of Unopened Returns With Identical Comments — Need Advice

For the past couple of months, I’ve noticed a pattern of suspicious returns on our account.
We sell shoes, and we’ve been receiving returned packages where the shoe boxes were never opened — the poly mailers are still sealed and untouched. Yet the return comment is always exactly the same on every single return!

What’s even stranger is that these returns come from different buyers, different states, and each buyer has only placed a single order. I don’t understand how or why this is happening, but it’s extremely unusual. We’ve been closely tracking this for the past two months and are seeing about 5 to 8 of these returns every week, though it’s very possible this has been happening for much longer before we noticed.

This situation is costing us a significant amount of money.

Do you have any advice on how we can investigate this or prevent it?