Well I spent hours scoping the internet, taking pics inside the hull and scratching my head.
Finall had enough and just sat down yakside with my tools and got working.
The cables seemed free enough and I could see no tangles inside so I figured the problem must be the drum itself.
Took the thing apart and no big deal. While it looks like go-go-gadget-kayak, it's pretty straight forward really. But I took happy snaps along the way just in case.
I think the problem was just that the pivot bolt was a little tight - might also have been some spectra doubled back and fouling inside the housing?
I noticed that there was a score mark on the outside drum where the hex head of the bolt contacts the drum and that means friction and that means resistance. I intend to place a plastic washer here to remedy this. Fortunately the design incorporates one inside the housing which should do the job nicely.
Thanks for the help guys,