I also as a Catholic was confused by Campion’s post. I think Campion misspoke there/didn’t write what he meant. I think he is referring to the non-essentials of the document (such as wording for example). Although the main issue regarding faith and morals is divinely revealed and therefore free from error it does not mean that the human who wrote it chose the perfect wording to explain it.
Hopefully he can come in and shed some more light on this, but I think this is what he’s driving at.
I applaud you attempt but none will suffice. Here is a phrase from that declaration. "is possessed of that infallibility with which the Divine Redeemer willed". The word "infallibility" must by definition include perfect "wording" as in without error. It's either infallible or it's not. As a comparison, God didn't say if a prophet was mostly right he was still a prophet. He said if just one of that prophets prophesies was wrong that prophet was not from God.
Sorry. I see damage control.
Free from error is free from error.
To say that the issue regarding faith and morals is divinely inspired and free from error, but error creeps in when it is transcribed, means that what the people are getting is NOT free from error.
At that point, it then becomes subject to interpretation and needing to be *correctly* interpreted.
At that point, there’s simply nothing that the pope can say, even ex cathedra, which can be trusted because nobody can know if it’s error free or where the error crept in.