Besides the inconsistent and poor quality of parts and removal of zinc from oil, lifter bores are more worn that they used to be from mileage. Lifter to bore clearance with a flat tappet cam is critical, and should be .0012" - .0018". If it is loose, or out of round, the lifters are less likely to properly rotate in the bore. This clearance needs to be checked, and rotation needs to be verified. If a flat tappet lifter doesn't rotate, it will fail promptly. If things aren't right, reamed/honed bores with oversize lifters (if available) or bushed lifter bores, or switching to roller lifters is the solution.