Mo. Rev. Stat. § 407.569: Affirmative defenses.

It shall be an affirmative defense to any claim under sections 407.560 to 407.579 that:

(1) An alleged nonconformity does not substantially impair the use, market value, or safety of the motor vehicle;

(2) A nonconformity is the result of abuse, neglect, or unauthorized modifications or alterations of a motor vehicle;

(3) A claim by a consumer was not filed in good faith; or

(4) Any other affirmative defense allowed by law.