Dave

Hi, no personal experienced of an issue with these, but the only things that spring to mind that may cause your problem are

a) cylinder over stroking for some reason
b)thrust bearing not accurately aliened with clutch causing radial forces on cylinder.

c)uneven fingers causing uneven forces on cylinder.

no simple explication for any of these, but worth considering.

can you dismantle a failed cylinder to see if there are any clues as to how it failed ?

cheers Aidan