How you deal with the SNAD is your own choice, I’m sure you know how eBay deals with them.
As for the legitimacy (or lack of) of your buyer’s claim, I have a few questions. Sorry if this offends you as it’s not my intention, I just need to be thorough in order to help.
Do you include anything in your package to try and freshen the smell? I sometimes get buyers spritz some sort of perfume, air freshener or put a dryer sheet in the box before they return it. Even unscented ones have a smell. Do you or anyone else in your house (where the items are stored) smoke? Not just asking about cigarettes but cigars, herbal stuff, or any other things I won’t mention? Is there incense or sage bundles being used. Pretty much anything that can have a significant aroma, fragrance, smell, or odor? Pets (I notice the photo as someone else pointed out), damp cardboard or newspaper, food? Yes, food. When I bought my house luckily I had to massive renovate it anyway, because the entire house reeked of curry. My agent and family all agreed, but the previous owner was totally oblivious to it.
I get a good amount of returns, and about 15% of them come back covered in pet fur and smelling like (what i hope to be) pet urine. When I bring it up to the buyer if they have a pet, a few buyers end up getting upset and defensive at me saying something like “I have no pets, just a dog/cat”.
So I understand how people can be oblivious about this stuff when they live with it everyday. I even have friends when hearing complaints about their smoke lingering on other people’s clothes say “Don’t worry, it’s just weed so it doesn’t linger as long as cigarette smoke”.
Your buyer MAY be looking thru your item with a fine tooth comb because he wasn’t able to get the original deal he wanted. And he might be thinking, if I have to pay that much for this item it better darn well be perfect in my eyes. So any small hint of a smell might set him off to file a SNAD.
