I also sell cuttings on eBay and know your frustration very well. Sometimes I have refunded money and other times sent additional cuttings.
This winter I took cuttings from my mother tree just before shipping, instead of storing a few dozen at in the fridge, thinking that would eliminate all complaints. Wrong!
I have come to realize that some buyers have no idea what to do with the cuttings when they get them, as they have not researched fig propagation, and expect you to provide all the information they need. I provide basic information including links to excellent sites.
They also don’t know what a dormant viable fig cutting looks like, even when you explain it to them.
I had just such a buyer this winter that lives about 15 miles from me. The cuttings were taken the same day as they went in the mail and were received two days later. There was no request for a refund; but they did leave negative feedback, because they were dry.
I improve where I can, and take note of each situation.
I think it just comes with the eBay territory.