I've only had an issue once selling on eBay.. the buyer claimed he never got his package but since I had tracking on it and it said delivered it was kinda hard to believe him.. eBay put his claim under review and decided to refund his money anyway but they let me keep my money too lol..
Now that I think about it, there was this other time when a different buyer claimed a pair of DS shoes I sold him weren't DS but nothing ever happened.
eBay always sends me special promotions to cap my selling fees at $20 or even half off.. also give me back a percentage of the sale in eBay bucks so I just keep selling on there
I've never sold on GOAT or stockx..