How do I fix driver's seat belt on 2004 Sienna that is stuck in full unrolled position?

Just bought a 2004 Sienna (toyota Certified) and have had it back 2 x now (in 2 weeks) for this same problem. Service Dept tells me this is not uncommon and it will jam if you "Pull it wrong"!!! If I have to go back a 3rd time...they better come up with a permanent solution as this is VERY dangerous.