IMHO, replace. I think lifters are not what they used to be, depending on the brand used in the rebuild. I only buy known brand names now - Isky, Howards, Comp or get a recommendation from Brent or Tim.
I'd be reluctant to replace the lifter now that the cam has been broken in using that lifter. Swapping the guts can be a problem because those parts are select fitted to VERY tight tolerance when the lifters are produced. This is what controls the bleed rate of the lifter. I think I'd put the lifter into the engine, crank up oil pressure and then adjust it to see if its working. Maybe it just picked up a little tiny piece of gasket, silicone etc.
I'd back Dave up on this.
Thanks for the advise. I will clean the lifter up as suggested,visually check bore,cam, oiling ,reinstall, adjust valves and see where it is.