Old type mechenical brakes

[oz argo]

I have recently replaced my brakes on an older 1992 Argo with new calipers and pads after only 8 hours of operation they have worn on the cam ball houseing , the alloy meterial they are made from seems very soft .I have owned this machine from new and replaced the brakes several times before and have not had the same problem .
Has anyone else had issues with the new brakes?