Insight, vol 1, under the heading "Inspiration", pp. 1205-1206, makes the statement that the Hebrew manuscripts were the inspired and inerrant pre-Christian scriptures. Yet it also makes the admission that the NT quotes of the OT weren't always verbatim quotations from the Hebrew text. At times the NT quoted the Greek-translated Septuagint, which, in some cases altered the wording and meaning of the quoted verse considerably from the Hebrew.
One such example given was "Paul's" quotation of Psalm 40:6 in Hebrews 10:5-6. Yet it reasons that, " God’s spirit guided Paul in his quotation, and therefore these words have divine authorization...those portions quoted by the inspired Christian writers did become an integral part of God’s Word." (p. 1206)
Yet, throughout the NT, when the writers quoted the OT and used "Lord" instead of the divine name, the WTS attributes the difference not to inspiration and "divine authorization", but to a lack of integrity of the existing NT manuscripts to the original. The ONLY justification given for such a conjecture is that the original Hebrew was not quoted verbatim.
But...didn't they say quotations didn't have to be verbatim to become "an integral part of God's Word"?
The kicker here is when they go on to say, " God’s own purpose in preparing the Sacred Scriptures and the inspired declaration that 'the saying of Jehovah endures forever' give assurance that Jehovah God has preserved the internal integrity of the Scriptures through the centuries.—1Pe 1:25." (p. 1206)
Just an observation.