I had a few of those handles. I didn't like the spongy feeling from the heavy cable, it'll flex differently at different times. Also didn't much care for the overhang. Flying with a Hot Rock felt better. I made up a couple hard point Hot Rock knock offs and sold the Brodak handles on Ebay. They're great for trimming, since they're so adjustable, but they're fairly rotten for flying the pattern consistently.
If I had to guess, I'd venture that the cable is pulling through the slider blocks during times of harder pull, and springing back when the tension lessens.