@Ehav4Ever already presented academic evidence here, so I'll bring his sources and some others as well:
From
Britannica:
"The name Septuagint (from the Latin
septuaginta, “70”) was derived later from the
legend that there were 72 translators, 6 from each of the
12 tribes of Israel, who worked independently to translate the whole and ultimately produced identical versions. Another
legend holds that the translators were sent to Alexandria by Eleazar, the chief priest at Jerusalem, at the request of
Ptolemy II Philadelphus (285–246 BCE), though its source, the
Letter of Aristeas, is unreliable.
Despite the tradition that it was perfectly translated, there are large differences in style and usage between the Septuagint’s translation of the Torah and its translations of the later books in the Old Testament. In the 3rd century CE Origen attempted to clear up copyists’ errors that had crept into the text of the Septuagint, which by then varied widely from copy to copy, and a number of other scholars consulted the Hebrew texts in order to make the Septuagint more accurate."
As you can see, errors had crept into the Septuagint. Origen tried to clear up mistakes - but that begs the question: What did he consider mistakes and what not?
From the
University of Helsinki's Septuagint Project:
"All the witnesses of the Septuagint of 2 Samuel ultimately stem from a single Greek archetype. The textual traditions were split into three branches: the B-text, the Majority text, and the Proto-Lucianic text. The B-text underwent the Hebraizing kaige revision perhaps the first century BCE. The Majority text shares most, but not all, of the kaige readings in B. In addition, one branch of the B-text has undergone another, later, Hebraizing revision that is commonly called “Hexaplaric”. Its notable trait are additions done on the basis of Origen’s (d. 254 CE) Hexapla, a multi-column work that presented a comparison between the Hebrew text, the Septuagint, and a number of other Greek versions. The Proto-Lucianic text attests to only a very small number of kaige readings. However, it served as the base text for another, much later, revision that bears the name of Lucian of Antioch (d. 311 CE)—hence the name “Proto-Lucianic”; the fully developed recensional text is called “the Lucianic text”. Because of the heavy revision, the Lucianic text on the whole is furthest away from the original translation. However, since its Proto-Lucianic base text contained very few kaige readings, the Lucianic text often retains the original reading when both the B and the Majority texts attest a kaige reading. This makes the Lucianic text a highly important witness especially in 2 Sam 10–24 (so-called kaige section) where the Majority text shares most of the kaige readings of the B text.
The edition includes:
A critically established Greek text that presents the closest possible approximation to the text that the translator produced.
Apparatus I, that lists all the meaningful variant readings in the Greek manuscript traditions, the significant readings from Latin and other secondary versions, as well as a selection of readings from indirect sources such as quotations from 2 Samuel by Greek and Latin patristic authors. The apparatus follows the well-established format of the Göttingen editions.
Apparatus II, that lists extant Hexaplaric readings derived from later Jewish Greek versions (Aquila, Symmachus, Theodotion). These readings can be found in the margins of the manuscripts and noteworthy indirect witnesses such as the Syrohexapla and ancient commentaries."
"The translator" is the person who translated the first ever Septuagint - as you can see, we no longer have that original translation, so much so that a special project has been set up to try to figure out what that original translation was like.
From
The Gospel Coalition:
"The term Septuagint is often thought of as the Greek version (or translation) of the Hebrew Bible, much like the Vulgate is the Latin version or the [Pesheeta] is the Syriac version. But, technically speaking, there is no such thing as “the Septuagint.” If you own a modern copy of the Septuagint (e.g., Rahlfs or Brenton editions), it is an “eclectic” edition, that is, a collection of the best and most reliable Greek manuscripts reconstructed to approximate the original translation of the Old Testament from Hebrew to Greek.
So, when scholars use this term, it does not refer to a single text. Rather, it refers to a collection of Greek translations produced by numerous scribes over the course of a few hundred years and, in all likelihood, composed in different locations. Today, the term is usually used to refer generally to the various Greek translations of the Hebrew Bible, as well as some additional books, such as Tobit, Maccabees, and Sirach, to name a few.""
As you can see, there were many different Septuagints. And if Origen, one of the most famous Church Fathers, and one of only two who knew Hebrew, noticed errors way back in the 3rd century, you should ask yourself: Why would there be errors? Clearly, these were inserted in by the various translators and copyists. Some might be simply scribal errors. But others? Well, that's a good question.
From
New Advent:
"On account of its diffusion alone the hellenizing
Jews and early
Christians, copies of the Septuagint were multiplied; a
nd as might be expected, many changes, deliberate as well as involuntary, crept in. The necessity of restoring the text as far as possible to its pristine purity was felt. The following is a brief account of the attempted corrections:
A.
Origen reproduced the Septuagint text in the fifth column of his
Hexapla; marking with obeli the texts that occurred in the Septuagint without being in the original; adding according to Theodotion's version, and distinguishing with asterisks and metobeli the texts of the original which were not in the Septuagint; adopting from the variants of the Greek Version the texts which were closest to the Hebrew; and, finally, transposing the text where the order of the Septuagint did not correspond with the Hebrew order. His recension, copied by
Pamphilus and
Eusebius, is called the hexaplar, to distinguish it from the version previously employed and which is called the common, vulgate,
koine, or ante-hexaplar. It was adopted in Palestine.
B. St. Lucien,
priest of Antioch and
martyr, in the beginning of the fourth century, published an edition corrected in accordance with the hebrew; this retained the name of
koine, vulgate edition, and is sometimes called
Loukianos, after its author. In the time of
St. Jerome it was in use at Constantinople and Antioch. C. Finally, Hesychius, an
Egyptian bishop, published about the same time, a new recension, employed chiefly in
Egypt."
From
SOTS:
"The translated books of the Septuagint were produced between the 3rd century
BCE and the 1st century
CE and were translated in varying styles. Revisions and new translations were also made over time, so that there is considerable diversity in the manuscript history of the Greek Bible."
"The first translations of Septuagint books are known in scholarly parlance as the “Old Greek” of those books. This term differentiates it from the revisions and new versions that arise in an attempt to improve the translations. Our earliest attested revision is that of the
Minor Prophets scroll found in Nahal Hever in the Judean Desert and dating from the 1st century BCE. This translation of the Minor Prophets is based upon the Old Greek, but, in similar fashion to the group of translations following strict adherence to the Hebrew, it revises the Old Greek towards greater consistency in Hebrew. Similar revisions can be seen in the manuscript traditions of other books, and in some cases (such as for
Judges,
Esther, and
Daniel) there are clearly more than one version in circulation.
Revisions continued throughout antiquity, and were attributed to significant figures in the early church (such as Lucian or Theodotion) or were preserved without attribution (as in the case of the A-text of Esther or the Barberini Codex). Aquila and Symmachus are two prominent Jewish revisers of the 2nd century CE, who translate in different ways but both adhere to the Hebrew and show an interest in its exegesis."
