This a very common problem. It used to be believed ALL these types of failures was do to dirt and debris etc, but I am here to tell you, not always the case. Sometimes a little more pre load helps, but more so, the industry is having issues with hydraulic roller lifters from several manufactures. Especially Comp and Morel. ( yes, Morel also) .I am in a group of engine builders on a private forum from across the country, and almost everyday, a hydraulic lifter issue pops up. I could write for hours about this. But here is my best condensed version. Buy Gatorman, GS Products,Crane or Johnson ( NOT Hylift Johnson).