Stuck focus ring (Vivitar 24/2.8)

[JDH]

Hey guys, I got my hands on a Cosina-made (C/Y mount) Vivitar 24/2.8 and I'd love to test it out, but the focus ring is stuck. I took it apart and as can be seen in the pics, there's whin metal ring holding the focusing ring in place, so I loosened the screws (not in the shot) and the ring can spin alright, but it doesn't move the focusing thread, so it just spins around with no effect whatsoever. Anyone knows how to fix that?