It will be hard to get your money back but of course they have to fix if it’s under warranty. I think it’s basically in their discretion to fix it or give you a new one, to an extent. If you want a new one it’s possible but if they don’t want to replace it you’ll have to put up a fight. If it’s a really bad defect then you might be able to get your money back but you’re probably going to have to sue them.