now that you've driven a 'good' motor a short distance and then had new problems, I agree with mm that we May not have considered pre-load.
However, I have to disagree about defective new units, when there have been multiple brand new lifters that will not even release any bubbles when soaking & stroking...
Does anyone think we should get the dissolved pre-lube out of there, with an oil change at only 2 hours runtime?
"pre-lube" applied out of the tube or squeeze bottle (no matter what the brand is) is nothing more than a very viscous form of a high quality lubricant with various extreme pressure additives. It's formulated to be totally soluble in engine oil while leaving the trace elements of the ep additives (zinc, moly, secret formula unobtanium, etc. Embedded in the metallic surfaces.
I personally run fresh motors a thousand miles or more before changing oil and filter. If it's suspected that there was trash left in the oil galleries, then cutting the filter open and performing an analysis will confirm that.
30w, 10w-30, 15w-40, straight 50w, no matter what viscosity oil is used, a lifter which is either not assembled correctly, is out of tolerance as far as it's individual components are concerned, or is "too short" in the entire valve train stack (including pushrod length, rocker distortion, rocker shaft wear, rocker stand height (entire rocker assembly) is not going to be able to work correctly and maintain a slight negative valve clearance/pre-load.
I've installed many hydraulic lifters over many years and had many act stupid for a given time period.
Wanna confirm rocker assembly "height"? Then swap rocker assemblies side-to-side and see if the affected cylinder/valve "moves".
Use the depth gauge portion of a dial caliper to ballpark the valve stem height of all valves (not just the problem child) once the rocker assembly is removed, and record the data for analysis.
There is a mechanical reason this problem exists, that can be rectified once it's identified, yawl just ain't found it yet and the shotgun approach is gonna eat ya up!
Has an attempt been made to collapse each valve/rocker/lifter using downward pressure of a hammer handle while the engine is running? If the lifter can be compressed fairly easily while under gallery oil pressure, then that is a problem and idle quality/manifold vacuum will go to hell immediately until the pressure is eliminated.