Contradiction with Genesis 6:5
This verse states that every imagination of the thoughts of man's heart was only evil continually, contradicting the notion of doing good continuously.
Genesis 6:5: And GOD saw that the wickedness of man [was] great in the earth, and [that] every imagination of the thoughts of his heart [was] only evil continually. [every...: or, the whole imagination: the Hebrew word signifieth not only the imagination, but also the purposes and desires] [continually: Heb. every day]
Contradiction with Jeremiah 17:9
This verse mentions that the heart is deceitful above all things, implying unreliability in doing good consistently as Proverbs 31:12 suggests.
Jeremiah 17:9: The heart [is] deceitful above all [things], and desperately wicked: who can know it?
Contradiction with Romans 3:10
It states that there is none righteous, no, not one, which contradicts the portrayal of consistent goodness in Proverbs 31:12.
Romans 3:10: As it is written, There is none righteous, no, not one:
Contradiction with Ecclesiastes 7:20
Asserts that there is not a just man upon earth who does good and never sins, contrasting with the idea of constantly doing good.
Ecclesiastes 7:20: For [there is] not a just man upon earth, that doeth good, and sinneth not.