Aha! I found a few on the WT Lib CD. They didn’t use errata but a different word, adjustments .
*** km 12/89 p. 7 Announcements ***
Some adjustments will be made in future printings of the Live Forever book. The only significant change is with regard to the Sodomites, on pages 178 and 179. This change appeared in the Revelation book, page 273, and in The Watchtower of June 1, 1988, pages 30 and 31. You may wish to note it in earlier printings that you have on hand.
Here’s the next mention of adjustment I could find:
*** km 9/06 p. 7 Announcements ***
The September Our Kingdom Ministry insert, pages 3-6, lists a number of adjustments for each one to make in his personal copy of the Revelation Climax book. This should be done in preparation for the Congregation Book Study starting the week of January 8, 2007.
Here’s that actual adjustment (errata). It is massive, probably the same as that link to our friend Atlantis' PDF file. I don't know for sure since I couldn't open that one.
*** km 9/06 pp. 3-6 Adjustments for the Book Revelation—Its Grand Climax At Hand! ***
Adjustments for the Book Revelation—Its Grand Climax At Hand!
Listed below are the key adjustments to the book Revelation—Its Grand Climax At Hand! which was published in 1988. This list does not include, for example, certain statistical adjustments, which can be found in the latest Yearbook and in other publications.
CHAPTER 4
p. 19, ¶4, delete last citation: Matthew 25:31-33
CHAPTER 5
p. 24, ¶3, replace footnote with: * For a detailed explanation, see the book What Does the Bible Really Teach? pages 88-92, 215-18, published by Jehovah’s Witnesses.
CHAPTER 6
p. 30, ¶11, lines 8-9, replace “2 Peter 3:1-3” with: 2 Peter 2:1-3
p. 30, ¶12, replace sixth sentence with: Finally, Roman Emperor Constantine gave state approval to the “Christian” religion, and this led to the development of Christendom, where Church and State joined forces in ruling for a thousand years.
p. 32, box, replace first paragraph with: Jesus was baptized and anointed as King-Designate at the Jordan River about October 29 C.E. Three and a half years later, in 33 C.E., he came to Jerusalem’s temple and threw out those who were making it a cave of robbers. There appears to be a parallel to this in the three-and-a-half-year period from Jesus’ enthronement in the heavens in October 1914 until his coming to inspect professed Christians as judgment began with the house of God. (Matthew 21:12, 13; 1 Peter 4:17) Early in 1918 the Kingdom activity of Jehovah’s people met with great opposition. It was a time of testing earth wide, and fearful ones were sifted out. In May 1918 Christendom’s clergy instigated the imprisonment of officials of the Watch Tower Society, but nine months later these were released. Later, the false charges against them were dropped. From 1919 the organization of God’s people, tried and refined, moved zealously forward to proclaim Jehovah’s Kingdom by Christ Jesus as the hope for mankind.—Malachi 3:1-3.
...
CHAPTER 43
p. 311, ¶19, replace sentences after citation “Revelation 11:15; 12:10” with: During the time of the end, the spirit and the bride have been inviting rightly disposed ones to take life’s water free. Water from this river will continue to be available to such ones right up to the end of this system of things and, thereafter, on into the new world, when New Jerusalem ‘comes down out of heaven from God.’—Revelation 21:2.
p. 312, ¶26, replace first two sentences with: Those trees, well watered by the river, may include the 144,000 members of the Lamb’s wife. While on earth these also drink of God’s provision for life through Jesus Christ. Interestingly, these spirit-begotten brothers of Jesus are prophetically called “big trees of righteousness.” (Isaiah 61:1-3; Revelation 21:6)
