My BA Falcon front seat belts would not retract tried washing them, scrubbing them, soaking them and still they wont retract.
After searching the internet found a post that suggested using a spray on dry lube, found that CRC make one which can be used on most surfaces, contains some special non grip chemical agent.
Bought a can from Bunnings $15 sprayed on back of seat belt and the guide above the re-tractor
the belt feeds through, 15mins later shes as good as a new one .

personally i would have 1st removed the belt base & cleaned it out as it most likely has dust & what have you blocking it from retracting.