I have a (new to me) 2002 Ford F150 Supercab. The front passenger seatbelt works fine until it is clicked shut. As soon as you click it shut it is locked and will not loosen at all, it WILL tighten but it won't loosen. When it is not engaged it is fine and when I close it with no one locked in it is fine. What could this be???

Thanks

Bleu