Any Testrite CS-3 Copy Stand Owners Out There?

Any Testrite CS-3 Copy Stand Owners Out there?

[My camera is a Canon 50D DSLR.]

I’ve owned a Testrite CS-3 Copy Stand ensemble for some time (years) but have never really used it as such as I may have a defective component.

The CS-3 setup includes - 18% gray baseboard (15.75”x 22.5”) … 2-part vertical post (38.5”) … adjustable “parallelogram” camera holder … and a small aluminum horizontal camera attachment.

It’s the last component that has me stymied. I can’t secure it via the vertical screw on the top of the parallelogram. Try as I may to tighten the screw (without breaking the plastic knob), the aluminum camera attachment continues to slide in and out freely.

Am I missing something ridiculously obvious, or do I have a bona fide defective component here? What are my workaround … or replacement options? Would contacting Testrite at this late date accomplish anything?

Thanks.