Cam gone flat? Here's a interesting video.

When installing new flat lifters / cam, one should always check that the basic machining characteristic that causes the lifter to spin as the engine is running is present.

1) place the cam side of the lifter against a very flat surface like a piece of window pane glass. Viewing from the side of the lifter down at the cam interface, the convex profile of the lifter should be apparent. The very center of the lifter should be pointed out with a very slight fall away to the outside diameter.
2) Place a straight edge across the cam lobs where the lifters contacts it. You will need to position the straight edge, so it is level and contacting two or more lobes at a time. Peering under the straight edge and maybe using a flash light you should be able to see the taper that is machined into the cam lob. With one side of each lob being higher than the other side of the same lob.

and lastly, I often wonder how many flat cam lobes that are wiped during break in are due to poor assembly practices, like verifying that the tappets spin with very light hand pressure at install. Lifter bore to lifter body clearance is pretty small. It would not take much soap scum or debris left in a lifter bore after a hot tank, or a slight nick on a lifter body due to carless handling to lock up a lifter and wipe a cam. The best oil and the best break in procedure will not overcome poor assembly practices.