That's probably because the mechanical rotary thingys in the door jam area are not engaged properly to the seat belt retractors. If you open your doors you will see what I'm talking about. They are located below the door striker. Someone may have removed them at some point and never reinstalled them correctly.
The lever is not broken but it's not installed correctly. I'm working on it now and Ican't seem to get it right. The red cylinder part is in the white nylon grommet thing but it wont retract. I'm wondering where the flat part of the red part needs to be aligned. I know this is a vague description, sorry.