Preaching is oral. How do you know what Paul preached? Got transcripts?
Well, yes, since the Holy Spirit made him the chief writer of the NT, and as these are the only wholly inspired transcendent and substantial records of what he preached, it is these that must judge all that is attributed to him.
To hold that what Rome says he or anyone else said via her amorphous "oral tradition" is the infallible word of God rests upon her novel and unScriptural premise of ensured perpetual magisterial. And what Rome claims to infallibly declare certainly is not wholly inspired of God.
We can see what Paul believed by his letters that were inspired by God. Do you have proof he preached contrary to what he wrote? Can you see what you must do to the Word of God, the Apostles and prophets to uphold a belief of your church? It must be worth it to you, but it does no service to the Lord.