Just for some clarification about the SSPX's view on the ordinary magisterium and heresy

So, it seems to me like the SSPX believes that Vatican II taught heresy, but it also seems to me like the ordinary magisterium, while not being totally infallible, would still be protected from teaching grave errors like heresy by the Holy Ghost. So just for clarification, since I'm truly considering taking the SSPX position but want to look more thoroughly into it, does the SSPX believe that the magisterium can teach heresy or would they just hold that modern magisterial statements and statements from Vatican II are problematic because they can be easily misunderstood as heretical?