Personally I have had super good experience with Gameloot. Have bought and sold multiple games/things. Once they even returned a disc which was not working at their cost. Only bad experience I had with them when I preordered Hotwheels Unleashed and they didn’t have enough quantities to serve the preorders. They didn’t inform me but when I reached out they refunded me to account.
My opinion is that all of us can have bad experience with any platform e.g. Amazon has not refunded $170 to me for a cancelled order even after couple of weeks. I have had multiple follow ups but no resolution.