I should have changed them 7 pages ago however I didnt realize you could get them in singles and thought you could clean the tick out of them. Ohh well.
Whenever you have multiple possible issues, you just have to try them out one at a time. Glad you got it.... proves once again that the current crop of stockish lifters are not very consistent. It did not used to be that way.
If I were you, I would pull the valve cover and with #3 ex on the heel of the lobe, see if all that slop is gone between the rocker & valve tip.
And yeah, some times cleaning will get them better, if it is just a speck of dirt in the check valve. I am suspecting that your bad lifter was either machined wrong and the piston was too low, or the piston would somehow jam down in its bore.