The religious leaders of Jesus' day didn't think that their traditions could contradict scripture either.Where does the Bible tell us that the church would be preserved from error and why do you think that the Christian church is protected from something that the Israelites were not protected from? Indeed, the writings of Paul were often motivated to correct errors within the church! God never promised error-free doctrines to either Israel or the church.
Not true at all... He told His Apostles (and Peter in particular) that whatever they bound on earth would be bound in Heaven ... He promised that the Gates of Hell would never prevail against His Church ... He promised to be with His Church until the end of ages. All these promises were not made to the nation of Israel. Perhaps your church is capable of teaching error. Mine is not.