Update:
Received the new XX1 cassette & XX1 chain from SRAM. Upon comparing the new to the cassette with 800 miles, I didn't see a huge difference in wear between the two, so I am now thinking there really isn't much wear on the original XX1 cassette. Also, I did not see any visual differences between the old and new, materials and plating all look the same so when SRAM says they made changes, they are not changes you can see with the naked eye.
I first installed the new cassette with the current XX1 chain that has maybe 100 miles on it. The top seven gears were smooth and quiet, but the lower four gears now had a bit of grinding. I adjusted the derailleur a couple time with no improvement, I removed and reinstalled the cassette, double check that I torqued it to 40 N-m but the bit of grinding in the lower gears was still there. Thought it was odd since it was just a few of the gears, yet every part of the drivetrain did not have many miles of use.
Finally I tried flipping the chain over just to see what would happen. I saw an improvement after flipping the chain but still has some grinding so I decided to install the new chain. At this point I have a new chain, new cassette, chainring with about 100 miles on it and r/d with about 100 miles on it.
Finally everything is smooth again. I take it for a ride on the trails, and wouldn't you know it, I am back to having my original issue with an occasional pop out of the rear of the drivetrain after shifting. The scenario is, I drop down a gear, I apply about a half to a full rotation of the crank, and POP! I get a clunk sound out of the drivetrain. It only happens once after shifting, doesn't happen again as long as I maintain the same gear. If I go up a gear, then drop back into the same gear again, it may randomly clunk or it may not.
On the bike stand, the drivetrain shifts perfectly. On the trail the drivetrain shifts perfectly, accept with I get a pop/clunk once in a while after shifting.
After all this, I just don't know what the problem is. It's just an annoyance, and SRAM has been great about swapping out parts for me but I'm to the point where I'm not sure what's left to do. I'm thinking I may just have to live with it.