Definitely internal...been twisting wrenches 50 years..I know what I heard...I'm on the verge of a rant..This is the second time I got screwed on a Chrysler product with an internal engine problem. Its not like buying a stale bag of potato chips...45k is not pocket change to me & from what I understand this is a design flaw, where a repair is the fix...There is no fix unless I'm missing something....
It could be lifters, it could be the exhaust manifold. I was "certain" that the ticking I heard on my '15 Ram 1500 Hemi was lifter tick. After lots of research, a lot of which was on this site, I learned about the exhaust leak that happens on the rear of the exhaust manifolds. And it sounded exactly like valve tick. To rule this out, this is what you check for. When engine is cold, reach in to find the nut holding the heat shield on the exhaust manifold...the furthest one back, on each side. If it's loose, or gone, you have a broken bolt, and the manifold is slightly warped, and it's leaking. And yes, after it heats up a little, it seals and the sound goes away. This takes about 30 seconds or so on a really cold engine.
I was ready to put in a new cam and lifters until I went out and tested those bolts. To correct it, I installed long tube headers.