I think there are several factors present on cam failures. For the most part, if you loose one lifter or two, either right after break in, or after several thousand miles, but after the failure, the rest of the cam looks good, that is either soft metal or improper machining on those lobes that failed, and the problem probably can be traced back to the break in. If the machining was poor or the metal was soft too much metals gets removed during break in, aggressive profile becomes even more of a problem, and a bunch of taper gets removed breaking in the cam, and it shortens the life of the cam, if those things are bad enough it won’t even last past the break in. It could have barely broken in also, and 10,000 miles later the same thing happens because the oil wasn’t doing it job either. The slow death…
If the cam breaks in ok, but it looses a lobe a few thousand miles later, but on inspection, the rest of the cam lobes look like ****, that likely a lubrication problem. Could be not enough taper on the cam too, but not likely, better chance of being an issue with lubrication. Most people don’t drive there cars enough anymore to find out there oil sucks. They just get the cam broken in and think everything is good. Lol