Locked Up Seatbelts

Hey In the process of redoing my interior I've swapped out my nasty tan belts for some nice blue ones. Here's my problem, both sets are locked up. I'm pretty sure my tan set was working in the vehicle (pretty sure i had my belt on when I drove it home), but now that its out they are locked up like when you are braking hard (will only feed a few inches of belt before it locks). My blue ones worked fine at the wreckers when I was taking them out but now they are doing the same thing. My question is, was this some sort of safety feature preventing amateurs from installing seatbelts themselves (sorry if thats a dumbass question)? What can I do to make them feed properly? Thanks a bunch!