I think your problem is a worn brass bus. Normally it’s your Pulley’s who are worn, but there where you just bought a new 100MM set, this ain’t possible. There where you tried 2 clutches, it COULD be possible it’s your rear 100MM disk (The one you slide over the clutch.)
Did you buy an whole new set, or just the disk which has the circlip mounted on it?
The problem is, Those clutches get easily worn because of damp weather The brass bus experiences resistance, and gets warmer and warmer. Eventually killing the clutch (or pully’s)
Hope you got something with this info ;).