Yes the mechanism may well be worn. Replacement is the cure.
BUT, have you followed the correct installation procedure? You need to slacken off the cable completely, then go to the primary side and remove the inspection cover. Release the 9/16" locknut and back it out a bit. Now screw the adjuster in until you feel it touching the pushrod. Back the screw out half a turn and set the locknut. Take up the slack in the cable and all should be well.
That's a strange looking cable though. I use Venhill Featherlight cables, they work great.
If that doesn't work, ask Bill "Hawaiian Tiger" if you can contact him. He's a good guy and I miss him.