Engine problems

This is the second time I have had this happen to me actually . Two different engines but same problem. This one happened to the jeep I am getting this week.

1990 Xj limited 4.0 Renix and the likes. Cam was swapped out to a cam that made more power midrange(previous owner did more road driving). The second lifter on the number one cylinder collapsed or something and broke the pushrod. In both of my engines I was about 3000 RPMS when it broke. i am lost on where to start diagnosing the problem that caused this breakage. Oil pressure was good the entire time, everything was fine.

Some background info that may help.

Valve job done when cam was installed
Freshened up at same time
Stock bore
stock oil pump
Head was ported and polished at same time.

Help me if you can.

The lifter could have clogged up and stuck or the valve could have got stuck in the valve guide . I have seen this happen before on a couple of Renix motors before both of them came in to the shop full of sludge under the cover . The valve got stuck in the guide due to lack of lubrication .

The first one it happened to was an HO era 1991 model. I know why it went because I was getting an oil light when it would get to the 2500 range.

Thanks for the help. Do you think I should just put all new lifters in it and put new push rods in it since it was just rebuillt or rebuild it all over again