Hello, i bought a ztto cassette and i did 800km the chain and also chainrings are new, chainring rotor and chain are ybn waxed (actually are 2), the deralleur Is an old generation slx, It keeb skipping on the 2/3 hardest cogs when i put something more of 600w sometimes also less, i hate also qnother sunshine cassette that Is new bit It works perfectly with the same setup (but hardest Gear i think Is 11), It could be that deralleur (most likely jokey wheels have play) the kmc link isnt good for that chain or the cassette Is bad, visually It seems ok but idk maybe i should shave some materiale somwhere but idk, in the next few days in going to test It with my other bike that has xtr deralleur and i know that Is perfect
Tbh i am tired to be so unlucky with bike parte lol (also from big game brands)