Of course, any thing we do is fallible, any time we think or act, we can fail to be perfect. But in the matters of Faith, the gift precedes our action, and the gift of Faith is infallible.
The gift of final perseverance is that of the proper use of the gifts (think talents) of Faith, Hope, and Charity; all gifts given freely to us by God Himself first, before any merit, before any effort on our part.
He established His Church as another gift to us, an instrumental cause of our salvation, to administer the Graces and to safeguard revealed Truth of Jesus Christ, agent and final Cause of our salvation.
It is really very simple, as He said, His yoke is easy, and His burden is light. His government is upon His shoulder.
This was already addressed and avoids the question. The gift of faith has both an object and a basis, (Rm. 10:17) and the basis for your assurance that Rome is the one true church, and thus your faith really is a gift from God, is the issue, which your posts have failed to actual answer from the beginning. .
He established His [Roman] Church as another gift to us...,
That is a mere assertion, and subjectively claiming the gift of faith is not the answer.