Question whether retention of repossessed property violated automatic stay turned on whether debtors had interest in car under state law; Bankruptcy Rule 7001 was implicated, and debtors’ contempt motion should have been brought as an adversary proceeding. Car seller/lender disputed whether title transferred to debtors before the petition. Seller repossessed before the petition then refused to return car after petition. Debtors brought motion for contempt, and seller defended that debtors never had an interest in the car. BAP dismissed contempt motion without prejudice to the debtors’ commencing an adversary proceeding seeking the same relief or alternatively seeking relief under § 362(k). “[I]t is error for a bankruptcy court to determine property interests outside of an adversary proceeding.”