Since the Catholics you're talking about are in fact the Apostles and those taught personally by them, as described in the Acts of the Apostles, "reasonable persons" will assume that some churches start out with sound Apostolic doctrine, and then fall into some degree of error.
ALL of the Epistles --- by Paul, Peter, James, John, and Jude --- have page after page of this kind of problem. That's why once-faithful congregations have to be corrected from time to time--- by the Apostles, their assistants (like Priscilla and Aquila), and their successors (like Timothy and Titus).
Or even Remedial Catechism teachers like --- ahem--- yours truly.
It's a tough job, but somebody's gotta do it!
Poor Catechism Classes Forever!
We taught ya the truth (assumedly); so why can't you keep it?