How do hydraulic flat tappet lifters fail?

Now what about the ends on this pushrod? Several are like this. Gritty like sandpaper.
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Is that the rocker end?
From the looks of that and the looks of the rocker in that one pic I believe you had a valve clearance issue somewhere. Either coil bind guides piston clearance something wasnt letting the valves open as far as the cam was trying to open them