Lifter refacing

Ive done some with a valve grinder. The 4th time i did so 2 lobes wiped out, filled the motor with metal chips. Complete tear
Apart and rebuild needed. Like the song says "three outta four Ain't bad"
Dont take the chance !
So the lifter failed? Were the cams new/used? Valve grinder maybe puts to rough of a finish on the lifter? Kim