Lifter replacement

I think the problem is the lifter piston it stuck in the lifter bore that is causing the problem.
after sitting a long time in the box they stick, I have always put oil in a tub, tupperware or something that will hold all 16 lifters filled with oil over the top of the lifters and then take a push rod and pump the lifter piston, when they are stuck tap the push rod with a hammer to drive the piston down, once loose pump it up. Make sure all lifters can be pumped and let them sit in the oil over night or till it's time to install them. On Chevy motors tighten the rocker till the push rod has no play and then go 3/4 to 1 turn and that gives you 0.060" preload on the lifter and I have never had a valve hang open or any other problem.