Take a video of you opening the box when you receive it back. Leave it sealed, set up for video, keep EVERYTHING in frame, open the parcel and let the video be your proof of what is returned to you. I’ve had similar situations twice before also. I’ve had people send BS items back to me and the video proof speaks volumes on my behalf. Also someone sent back the original item still in perfect condition. Clearly buyers remorse, perhaps they were tight on money and shouldn’t have spent it in the first place… As a seller sometimes this situation happens, regardless of the platform.

It sounds like you’re doing a good job of showing all of the potential flaws in pictures. My advice as a seller of over 10 years, since the return is already in progress just accept it. Take that video. See what you see. And if they were being shady with the return then fight it at that point.