Have I? Let us see.
You must know very well that they have made declarations of the infallible, God-inspired, error free Holy Scriptures and assert exactly that in the Catechism you "say" you uphold.
I have been corrected twice here on FR where I differed from the Catechism and have thankfully and publically posted that acknowledgement.
You apparently are stuck on the problem you think you see in differing accounts of the resurrection morning and, in truth, it is no more mysterious than voicing the viewpoints of the different people who gave their own accounts to the writer. No retelling of a real event is ever in perfect sync between various people and, if they were, it would prove a prior conspiracy between them to all tell the exact same thing. This, by the way, is a good way police investigating a crime can judge the truthfulness of the witnesses. No one person sees everything it exactly the same was as another especially not when they happen upon a scene at different times.
There is a difference between infallibility of interpretation and infallibility of text. You claim infallibility of text. Well, let's have it. What is written, infallibly, over the head of Jesus on the Cross? No waffling this time, please.
Your own Magesterium holds that the Holy Spirit "breathed" the very words to the hearts of the writers of Scripture, yet you state time after time that you STILL cannot come to terms with what you say are "discrepancies", which is only a slightly nicer way to say errors or contradictions.
Inspiration is not dictation. Scripture is only as good as fallible men have received and acted upon the inspiration. We are not the robots of the Reformed who can only do what is programmed. God does not dictate; He inspires. He breathes; we receive and interpret what is breathed. Unless we are perfect (we Catholics are not), then we receive imperfectly. Do you claim personal infallibility?
On this point I am closer to the doctrine of Scriptural integrity of your Magesterium than you are. How did THAT happen?
In the light of day, I don't think so.
I have no need for "waffling". Why do you need to refuse to accept plausible explanations for what you say are errors? Is it because you NEED to accuse the Scriptures of fallibility so you can transfer its true contents to an "infallible" Magesterium to illuminate the Scriptures for you? Are you aware that the Holy Spirit is in us to reveal the truths of Scripture to us? Here is another explanation that, to me, sounds entirely "plausible". Try this on for size. From http://www.errancy.com/what-did-the-sign-on-jesus-cross-say/:
Modern standards for direct quotation do not apply:
What has to be the case for a statement to be true depends on the statement's meaning. Meaning is determined by more than just the words used; this is why "the door's over there" can be an instruction to leave rather than just information about the location of the door. (Among the factors that affect meaning are context and convention.) You can't always tell what would have to be the case for a statement to be true just by looking at the words that it contains.
Literary conventions about precision in direct quotation have varied over time. Although now we'd say that "Friends, Romans, countrymen, listen up!" is a misquotation, by other standards (e.g. by biblical standards) it would be fine because it accurately captures the meaning. The same quotation can thus be either accurate or inaccurate depending on what conventions are in play.
If we read the biblical verses above bearing in mind that they were written before there was a literary convention that direct quotations should be word-perfect, they don't make any claims about the precise wording of the sign over Jesus. All they make claims about is the meaning of the sign. All four descriptions of the sign agree about its meaning, even if they use slightly different words to express it. This is enough for us to judge that the gospels agree as to what the sign said; the minor differences aren't a problem for inerrancy.
The sign said ‘This is Jesus of Nazareth, the King of the Jews’:
Quotations don't have to be complete to be accurate. To quote Shakespeare accurately, it isn't necessary to quote an entire play, a couple of lines will do. Similarly, to quote the sign over Jesus accurately, it isn't necessary to quote the whole thing. Each of the authors of the gospels gives us part of the text on the sign. By combining their quotations, we can see that the whole thing read "This is Jesus of Nazareth, the King of the Jews".
There were three inscriptions in three languages, each worded differently:
John tells us that the sign over Jesus was written in three languages: "Many of the Jews read this inscription, because the place where Jesus was crucified was near the city; and it was written in Hebrew, in Latin, and in Greek." [John 19:20] In each language, the wording of the sign was slightly different.
Matthew gives the wording of the sign in one language; Mark and Luke give it in a second language (with Mark omitting "This is", but accurately preserving the sign's substance); John gives it in a third. All four accounts thus accurately describe the wording of the sign, despite the differences between them.