The right rear seatbelt of my '97 E420 became stuck in position. I removed it and tried to unlock the mechanism but couldn't. Dealer price for OEM is $200 so I took my trusty tools to the local "u-pullit yard" and got one from a '00 model. It worked fine out at the junkyard (pull it out and it would reel back in) but as I was installing it in my car this s.o.b. became stuck. Any idea how to unlock the mechanism?