Seat belt retractor

Hi I have a 74 dart sport and I got to bring it out for the first time after buying it and redoing body and drivetrain the seat belt retractors you really have to play with to get them to come out and if you don't keep pulling them out they stop and then you have to mess with them all over again sometimes they will not come out at all what it causing this and how do I fix them both sides do the same thing TIA