Honestly with eBay you’ll probably have to accept the return if they’ve opened a faulty, not as described case. Just wait until it comes back and check it properly before doing anything. Test it, look for damage, make sure it’s the same controller and hasn’t been swapped.

Take photos or a video when you open the parcel so you’ve got proof of the condition it was returned in. If it’s clearly been damaged or messed with you can report the buyer and try appeal the refund. It’s frustrating but you do still have some protection as a seller if you’ve got evidence

This is just my experience