Sorry - I haven't owned a Tracer myself. Never had a problem with the Universal nor the Graham Phantom or VPI Fatboy which seem to have a similar counterweight adjustment mechanism. Sounds like the adjustment knob is mounted on a threaded rod, and it's not been properly secured. I might try either of the following, using "firm" forces but not enough to risk any breakage:
1. adjust counterweight all the way clockwise, and then tighten firmly so it has enough "grip" to move counter clockwise again.
2. push against the counterweight (oppose its motion) as you move the adjustment clockwise so the turning knob has a chance to better grip the rod.
Perhaps the rod threading was meant to have some minor adhesive which failed, but that's speculation. I'd definitely recommend emailing Musical Surroundings (Clearaudio NA Distributor) for their thoughts - they've always been very helpful and responsive to me.