It's been a while since I bought my last set of cards but nothing has changed. A few months ago, one of my cards zeroed out. I told Sofia and he immediatly replaced it and appoligized. Today, I sent first and recieved a working card within 10 minutes. Smooth transaction.

Tl;Dr:
Sofia's warrenty is legit and he is a seller who values his reputation and deserves all the trust he receives. Thanks again ^_^