I finally changed all my clutch parts last year, but before I did, there was a suspicion that the pivot had started to loosen.
I originally installed the pivot back in the 1990's and it wasn't easy. The countersunk rivets come through the pressure-plate from the outside and it's difficult to peen them over on the inside. Try swinging a hammer in a bowl. I heated mine so that after peening, they would shrink tighter.
Anyway, mine turned out to be fine and I noticed the pivot was very thick steel. Nonetheless, my clutch book does mention about the pivots cracking and show a fix.
No doubt after welding the gussets in, peening rivets would be very difficult. I see that pivots often come now with countersunk (allen) bolts and nuts.
It appears you have no recourse other than to take the clutch out which is quite a job in an ERA. You'll find out what's wrong then. If you're really curious, you may be able to see through the clutch fork bell-housing hole with a flashlight, or better still, a boroscope.
