Yeah open pressure way too high.

Something I have always done (that I learned from a guy who built 1950's champion NASCAR Hudson Hornet engines...believe it or not) was to take the lifter bottoms and lightly etch them in a figure 8 on a piece of glass using jewelers rouge as an abrasive....he said it micro etched the machined surface to help it retain oil on the mating surface....just wipe them clean with mineral spirits and use GM eos at break-in. He said they break in almost instantly.

Well I always did it on all my flat tappets over the years...and I never lost one even running fairly high spring pressures...not 400 but mid-ish 300's.

Sometimes the old ways are the best