My '21 Yukon Denali had both lifter issues start at approximately 26,600 miles, then the 2nd one at 27,000. I remember an old vintage car I had as a "learn how to fix it" (old Mercury Monterey with the slant back window that went down) and the lifter sound was LOUD... Anyway - I heard that sound in the NEW engine on this gorgeous '21 and could not believe my ears. The dealership rep started with the "oh, we were sent the wrong parts last time" when they said they changed all of the lifters (same b.s. that others have written - same exact line). We barely went an hour's distance and then it happened again. So, it's been there TWO WEEKS now... I read them the riot act that the CAM needed to be changed, the fuel pump, oil, oil filter... Three days later (today) the dealership called back saying the problem WAS the CAM (I don't believe that either - they are grasping at straws!!) I had told them that my mobile mechanic that comes to my house for our other vehicles said to demand the CAM be changed and all the rest listed above because shards of metal could be floating around and further damaging the engine. I leased this SUV so I intend to invoke the lemon law, but first have to figure out where to start on that. Do I go to the Bureau of Automotive Repair first? Do I just go to the dealership I bought the car at? (different from the dealership I go to for repairs since it's closer to home) Call the lease company? I want the $$ back I've spent on a car payment when it's been in the shop for 3 weeks already, my insurance, OnStar, Car Wash pass, Sirius XM, and my original deposit... it's my business vehicle! Haven't read up on the '22s yet but the '23s should be coming around the corner mid-year. The '22s don't have the rear entertainment feature - probably due to product availability...
Frankly, from what you describe, it sounds like your dealer actually doesn't know what they are doing. Based on what you describe, it sounds like they did something wrong with the first lifter swap (like maybe using the old lifter trays or even aftermarket lifter trays, perhaps to get you out the door sooner if OE units were on back order) and you wiped a cam lobe shortly after the first swap.
One thing that argues for your dealer maybe being a little out of it is the swap of all 16 lifters at the 26,600 mile mark as GM's TSB directs them to only swap the bank of lifters with the bad lifter if the engine has more than 8,000 miles on it (nutty I know, but that does seem to be GM policy).
In general, a failed DFM lifter doesn't damage the cam as the lifter keeps riding happily along on the cam lobe, it just stays in "DFM active mode" (i.e. collapsed) even when DFM is turned off causing the hard misfire in that cylinder. Occasionally it seems the DFM lifter will jam in the collapsed (or partially collapsed) position, perhaps from a piece of the broken lock pin spring that is the faulty part on these bad lifters (i.e. not expand/collapse as the lobes come around and goes past), and the push rod that damaged lifter will fall out of its cup in the rocker and subsequently can jam against something solid like a rocker tower and result in a bent push rod, but I haven't read many accounts where the cam was damaged because of a failed DFM lifter (or AFM lifter in past generation engines), that just isn't how it works. That is why I say it sounds like your dealer screwed up the first swap, especially of the cam was damaged in the second go round.
Anyway, it sounds like you have a good plan in that lemon law return approach. I think if you do run into enough problems getting a fair return price on your truck that maybe you decide to live with it for a while, I would probably try to find another dealer with perhaps a little more competent shop going forward. I am lucky that the shop I use at my local dealer is fortunately really competent, so I don't worry about repairs they do. Ironically the sales department at the same dealership is as sleazy and incompetent as any I have ever seen. I do think it is a pretty random thing, the competence quotient dealer to dealer.
Anyway, good luck with whatever ends up happening.
