My $64 dollar question is about the Masoretic texts. They were retranslated by Judaic Jews in the 8th and 9th century AD if memory serves.
They were already in Hebrew, so there were inherently no retranslations.
What the Masoretes did, as far as I understand, was two things:
1) Make an effort to better standardize the text
2) Add vowel pointers
I should explain the issue of vowel pointers. Originally, Hebrew wasn't written with vowels, just consonants. You just knew the pronunciations based on oral communication and context. Thus, nothing in the Bible ever had vowel pointers when it was written. Later on--in the second half of the first millennium AD--a system of vowel pointers was created, which were little symbols you would put around the letters to show what the vowel pronunciations were supposed to be. The Masoretic Text includes those, and they became a feature of the Hebrew language going forward, though a lot of time they're left off in Modern Hebrew.
The vowel pointers, beyond being a pronunciation aid, can also differentiate words. Much like the word "wound" in English, which has two separate pronunciations with very different meanings (compare "I have a
wound from my injury" to "the clock is
wound up", where the word has a different meaning and pronunciation in each sentence), you can have words with the same letters, but different vowels, giving you different words.
One of the goals, as I remember hearing, was to shift translation away from interpretations that Christ fulfilled ancient prophecies, changing in places “virgin” to “young woman” where the vowel markers permitted.
I assume you are referring to Isaiah 7:14. The question of whether it should be translated as "young woman" or "virgin" is a debated point, but the question has nothing to do with the vowel pointers nor even the letters themselves. While some words change meaning if they have different vowel pointers, as noted above, this does not seem to be one of them. So while there are some cases where someone could try to argue they made an error with the vowels and they should have put in different vowels to give the word a different meaning, this isn't one of them.
It is also not a case of them changing the word itself in the creation of the Masoretic Text, because the Dead Sea Scrolls, done prior to Christianity, have the same Hebrew word in Isaiah 7:14. (I confirmed this with the useful book "The Dead Sea Scrolls Bible", which gives a translation of the text of the Bible as can be reassembled from the Dead Sea Scrolls, including notes of differences with the Masoretic Text, and there is no mention of this word being different).
So there really isn't any controversy over what the original Hebrew word was. The controversy is over the appropriate translation of it. But that doesn't have anything to do with any change in the text itself.
Have any issues ever been raised over the canonicity from the Orthodox perspective of the Masoretic texts, translated by people who denied our Faith?
Well, as noted, they weren't translated, as they were already in Hebrew. Well, as noted, they didn't translate anything. The works were already in Hebrew. The question is whether the readings they kept were the accurate ones.
Can't really comment on the Orthodox perspective, but I know I have seen some Christians express dubiousness over the Masoretic Text for this reason, namely it being maintained by people who rejected Christianity. The Dead Sea Scrolls do predate Christianity (and thus any rejection), but due to the fragmentary nature of the DSS, there's a whole lot of verses in the Old Testament that aren't available in them to check.
