I quote below from Bible:
Genesis 7:1
Noe with his family go into the ark. The deluge overflows the earth.
[1] And the Lord said to him: Go in thou and all thy house into the ark: for thee I have seen just before me in this generation. [2] Of all clean beasts take seven and seven, the male and the female.
http://www.drbo.org/chapter/01009.htm
Genesis 7:1
1The LORD then said to Noah, “Go into the ark, you and your whole family, because I have found you righteous in this generation.
http://niv.scripturetext.com/genesis/7.htm
Genesis 9:9-12
[9] Behold I will establish my covenant with you, and with your seed after you: [10] And with every living soul that is with you, as well in all birds as in cattle and beasts of the earth, that are come forth out of the ark, and in all the beasts of the earth.[11] I will establish my covenant with you, and all flesh shall be no more destroyed with the waters of a flood, neither shall there be from henceforth a flood to waste the earth. [12] And God said: This is the sign of the covenant which I give between me and you, and to every living soul that is with you, for perpetual generations.
http://www.drbo.org/chapter/01009.htm
Genesis 9:20-22
[20] And Noe, a husbandman, began to till the ground, and planted a vineyard.
[21] And drinking of the wine was made drunk, and was uncovered in his tent. [22] Which when Cham the father of Chanaan had seen, to wit, that his father’ s nakedness was uncovered, he told it to his two brethren without.
http://www.drbo.org/chapter/01009.htm
- Noe was righteous and for this he was chosen and a covenant was made with him.
- It was promised that there would be no more floods in Earth after the deluge.
- Nakedness was a sin and Noe got drunk and became naked; it was his fault; but he was not punished and yet he distributed his blessing to his favorite son.
Floods did not cease even after the deluge; the covenant was not fulfilled. Noe did not remain innocent and became sinful, as stated in the Bible.
Obviously, it is the scribes who tried to make Noe sinful while he was an innocent person.
Hence, Bible is not preserved in its original form. Genesis is not covered in the warning of the revelation which is specific, if at all, for revelation and cannot be extended generally to other books.