Yea that happened to me when i took my entire interior out. If you carefully remove the plastic cover that contains the retracting mechanism, there are little plastic gears with a plastic "pick" that jams into the teeth when A) it is pulled too hard, as in hard braking, or B)is not held at the correct angle (it has a little metal weight that seats when the seat belt tensioner is held at the exact angle that it is being mounted.)
What you have to do is make sure you get the L and R sight correct, then mount it, if it still wont go you have to pop the cover off and relocate the weighted self centering jamming plastic pick untill you get it right so it will seat on itself and retract allowing for full retraction of the belt.
How long did it take me to put them back on and have them working again you may ask?
Took me about 7 beers to figure it out mang.
Hope it helps, just be patient lol