I was at Mats house the other day looking at these.
It appears that after years of fat arsed blokes bouncing up and down on them that the ball bearings
seem to develop little flat spots and instead of rolling in the rail they slide and the ball bearing carrier gets stuck on the rail stopper
preventing you from getting those 2 extra spots.
i fiddles with it for about 15 minutes and diagnosed it as f$%@ed.
Hi seat also only did this once he took it out and out it back in ..weird eh?
Cheers Doug