Tighten van den Hul RCA Connectors?

I have these interconnects, the Combination Hybrid:

http://www.vandenhul.com/p_B06.aspx

The RCA connectors are making a slightly loose contact on both amps I have tried. The connectors look like this:

http://www.hifigear.co.uk/product_images/vdh_wellhybrid_curl.jpg

Any one ever tightened these?