Is there some inherent flaw with hydraulic lifters on this engine, or is it just part of the rash of cheap Chinesium that flooded the aftermarket several years ago? (I suspect the latter).
Meanwhile, you could also get a borescope-they're remarkably cheap these days-and look down into the cylinders and see if the walls are fresh. Probably what's happening is you've got a stuck valve from sitting, and once it barks off it'll free up.
