Jaymac, these little things can try ones patience I agree.

The issue is that they come with 4.5mm cord and its not available in Aus, well not the original stuff anyway. The size we get here is 4mm and next step is 5mm. I have tried 3mm, 4mm and 5mm. The best stuff is what you have from Reg

You have by the looks of it the Reg supplied stuff and that works OK, and yes the cord doesn’t last that long, before it starts to slip, at about the time you have say 30% tension on it. If you can get above the 30% it starts to work OK once again.

So what to do dilemma for people who have these.
Elmo will back me on this as he has some as well, (I have two)
The serrations on the wheel need to be dressed say at least once a season, about every 3rd serration, (profile to be sharpened and not dull edged) don’t do them all. (Dremmel Kit from Bunning’s will do this)
The cord, when it starts to slip, reverse it in the system (change end too end) as it is only a short section that gets the crap flogged out of it.
Also try lining up the cord through your sail pulley so it crosses over and gives a bit more of a direct pull across the serrated section (runs down around pulley with cord at an angle that brings pulley and cord into max contact) If the sail pulley sits out away from down haul, the angle of attack is just enough to let the bloody thing slip.
They are great when they work, but a bloody big pain in the coit when they give problems. Clean cord in fresh water so they dont go hard with salt impregnation.
Hope this helps.
You dont want it, throw it my way

Or you see me at Lucky Bay, give me your old pulley, and I will clean it up for you.