No stablecoin issuer is going to tell you that their stablecoin is not backed by what they say it is backed by. So there is risk with every stablecoin, because you cannot verify if they are truly backed 1:1 or they just print so many of them anytime they want to, pegged to nothing but thin air. Mind you as well that stablecoins can be frozen by the issuers anytime, in any wallet, these are the reasons why stablecoins should not be held for the long term.