Ebay selling related terror

Soo I've sold a few things on evilbay before - nothing for megabucks, don't really expect bjd kind of cash for my paltry items. But frankly it's a way to clear space without Smother's hoarding getting too irrational.
Thus far everything's gone relatively smoothly, but I've just run into one of the reasons why the site is called EvilBay. My most recent sale is raising alarm bells. Especially galling about the terror of a possible negative feedback situation since it effectively went for charity shop money!
Slightly suspicious ebay message asking for item number on outside of the box. ...And there's the company name/purpose, which in no way was indicated by the ebay ID. They're a broker who sells to Japan, and go by the name Shop Airlines Europe B.V.
I'm not too bothered by the fact that they're a broker. However they're infamous for... Several weeks after the transaction giving neg feedback and demanding a full refund.
Effectively pushing their international shipping liability onto the unawares seller at the other end who had thought they were selling to another human being rather than a middleman. Despite paypal rules stating that seller liability ends when the item arrives at the initial destination.
Any advice for preemptively covering my ass on this - given that ebay is somewhat infamous for siding with the buyer every time? I can't really back out of the sale since they've paid already, and I suspect cancelling the transaction at this point would result in automatically getting -ve feedback. (Tempted to send the item tracked despite the fact that they did not pay/ask for it. But then that would likely translate into negative money given UK shipping costs) I'm not even entirely sure how to contact evilbay to ask them - none of their online options seem to cover this sort of thing, and I dread the fed-up call centre worker.
However - despite all of the above hearsay, the Ebay ID in question somehow has 100% positive feedback. Sooo do as they ask and just document absolutely everything?
Urgh I just hope my next batch of evilbay items doesn't attract another infamous buyer in disguise!
Thus far everything's gone relatively smoothly, but I've just run into one of the reasons why the site is called EvilBay. My most recent sale is raising alarm bells. Especially galling about the terror of a possible negative feedback situation since it effectively went for charity shop money!
Slightly suspicious ebay message asking for item number on outside of the box. ...And there's the company name/purpose, which in no way was indicated by the ebay ID. They're a broker who sells to Japan, and go by the name Shop Airlines Europe B.V.
I'm not too bothered by the fact that they're a broker. However they're infamous for... Several weeks after the transaction giving neg feedback and demanding a full refund.

Any advice for preemptively covering my ass on this - given that ebay is somewhat infamous for siding with the buyer every time? I can't really back out of the sale since they've paid already, and I suspect cancelling the transaction at this point would result in automatically getting -ve feedback. (Tempted to send the item tracked despite the fact that they did not pay/ask for it. But then that would likely translate into negative money given UK shipping costs) I'm not even entirely sure how to contact evilbay to ask them - none of their online options seem to cover this sort of thing, and I dread the fed-up call centre worker.
However - despite all of the above hearsay, the Ebay ID in question somehow has 100% positive feedback. Sooo do as they ask and just document absolutely everything?
