i encounter this problem a month ago and the only way to solve the problem is to replace new lens and if your ps3 still under warranty than i suggest you return it back to sony for replacement.
I got mine from consoleparts4u worked perfect was only 25 pounds. Just remember dont mess with the gears when its open so it fits back the same as you opened it. I had to strip mine down and re do the mech because of gear mesh.