Most Church Fathers regarded the Septuagint as the standard form of the Old Testament. When the Councils of Hippo (393 AD) and Carthage (397 AD) set the canon of the New Testament they also confirmed the Septuagint as the Old Testament. Further evidence of the Septuagint's acceptance by the early Church can be found in the New Testament itself. It quotes the Old Testament approximately 350 times. Three hundred of those quotes are from the Septuagint. Surely this amounts to an overwhelming endorsement by the early Church.
Some raise objections over supposed errors. One example is in Judith 1:1-7. Here Nebuchadnezzar is called the king of Assyria when in fact it is well known that he was the king of Babylon. But Judith is not a historical book; it's a religious novel. The combining of the Babylonians and the Assyrians is a representation of the enemies of Israel. Both had conquered Israel at one time or another. Judith means Jewess and she represents the whole of Judaism. The lesson of the book is to rely on God's way of deliverance no matter what the method. Similar objections are raised over verses in Tobit, which are likewise symbolic and not historical.
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BTW, I did not realize that you are not a Catholic. You are an excellent apologetist ... kudos!