How do I un-jam my seat belts? Help!

MOPAR faithful: Have you had this problem? Your seat/shoulder belts jam as they extend when you're buckling up. My 74 Duster does this all the time. They eventually lock up to when the seat belt and shoulder harness are completely stuck and will neither retract nor extend. Anybody know how to fix this? Maybe lubricate something in the retractors? I can't figure it out. Thanks - BOB