How do hydraulic flat tappet lifters fail?

I’m halfway kidding because Rusty helped out last year when I had to rebuild it. He knows this engine has a history, and I suspect he might not think the original problem was fixed.

All the lifters and rods are out, except for the #1 intake lifter. It’s mushroomed a bit and will need to drop out when I pull the cam. I had all the lifters and rods lined up in order until the damn dogs ran across them. Now I have no idea which came from where! No matter, I’m replacing all anyhow. But I did want to be able to inspect the wear in respect to where they came from. I do know one of the lifters from #7 looked funky on the cam side.

The cam will likely come out tomorrow, assuming I can get this damn damper puller to work. Initially I was going to just inspect the rod and main bearings and replace if necessary, but now I’m thinking I might just replace them anyway and not take the chance. They’re too affordable and too important to not just do it.
im no professional but a lifter should not be mushroomed to the point you can't get it out after 600 miles. That's some serious heat. Was the mushroom one on one of the bad lobes? I have seen carbon buildup stick a lifter in the bored before but not after 600 miles sounds like a oilling problem mixed with some bad geometry lol.
The way measured my preload was put the expandable pushrod in with the lifter and lobe in the valve closed position screw it up till it touches the rocker and takes the lash out. Then remove the rocker measure it and compare it to your pushrod it should be .02-.06 longer than the adjustable one