Contradiction with Galatians 5:24
Romans 8:12 suggests obligation to resist the flesh, while Galatians 5:24 states that those who belong to Christ have already crucified the flesh.
Galatians 5:24: And they that are Christ's have crucified the flesh with the affections and lusts. [affections: or, passions]
Contradiction with 1 John 3:9
Romans 8:12 implies a struggle against the flesh, but 1 John 3:9 says those born of God cannot sin, implying victory over such struggles.
1 John 3:9: Whosoever is born of God doth not commit sin; for his seed remaineth in him: and he cannot sin, because he is born of God. [is born: or, has been born]
Contradiction with Romans 7:15
Romans 8:12 suggests control over the flesh, whereas Romans 7:15 depicts a lack of control over fleshly desires.
Romans 7:15: For that which I do I allow not: for what I would, that do I not; but what I hate, that do I. [allow: Gr. know]