Help Diagnosing Sound

[GSXDNA]

Immediately following a pull today, my car started stumbling really bad and making some rather loud knocking noises. The knocking is not consistent, and doesn't follow a particular rhythm. I've been told one (or more) of the lifters may have failed. I pulled the valve cover off and wasn't able to get any of them to move with force, but I'm not sure what else I should be looking for. Video below. Any help is much appreciated.

VIDEO:
https://goo.gl/photos/yfbH7xvn8EkuWoHa9

 

[ThunderChild]

Almost sounds like a follower or two with flat lobes, or maybe a diagonally cracked cam?

Maybe not the cam...how about your springs and retainers, any visual issues? A collapsed lifter or two would make alot of sense

 

[GSXDNA]

I can't see any visual issues with the springs and retainers - then again, I don't really know what a problem with those would look like.

Would I only be able to detect a problem with the lifters if the cam lobe is all the way up? I don't yet have the socket to turn the cam gear, so I just turned the car over a few times, then re-checked each lifter in various positions. But, I certainly haven't checked each one in the fully extended position. My assumption was that if the lifters were the culprit, I'd probably be able to detect that without the lifter fully extended, but maybe that was a false assumption.

 

[GSXDNA]

I found the issue. The adjustable cam gear bolts came loose, so the exhaust cam was sliding all around. Applied some locktite, re-torqued, now it runs great.