When I was proudly wearing the uniform the CO needed to pull you into his office just ONCE, before you got the message that not fulfilling your obligations wasn't going to fly in his squadron.
I would contact the soldier's Company Commander or Legal Affairs unit to see if this can't be cleared up so it doesn't hinder his/her ability to focus full time on defending our country.
As for the SSCRA - Section 531 Installment contracts for purchase of property makes it clear (to me) that you can not repossess the property (auto in this case) except by action in a court of competent jurisdiction.
Sec. 531 Installment contracts for purchase of property.
(1) No person who has received, or whose assignor has received, under a contract for the purchase of real or personal property, or of lease or bailment with a view to purchase of such property, a deposit or installment of the purchase price, or a deposit or installment under the contract, lease, or bailment, from a person or from the assignor of a person who, after the date of payment of such deposit or installment, has entered military service, shall exercise any right or option under such contract to rescind or terminate the contract or resume possession of the property for nonpayment of any installment thereunder due or for any other breach of the terms thereof occurring prior to or during the period of such military service, except by action in a court of competent jurisdiction.
Good Luck.